Right. I found the log interface, and it seemed like a good idea to switch on all the debug options before recreating the bug.
From what I can tell, it seems like the service tries to establish a connection to the phone using both IPv4 and IPv6. That is the only sense I was able to make from it all, but I thought it might be worth a mention. Here is the readout from what appears to be a couple of crash-restart loops:
Summary
2018-08-13 00:37:24 http: GET "/rest/events?since=80": status 200, 3 bytes in 60000.32 ms
2018-08-13 00:37:24 http: GET "/rest/events?since=80": status 200, 3 bytes in 60000.25 ms
2018-08-13 00:37:26 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A24.365062262%2B03%3A00": status 200, 5930 bytes in 0.59 ms
2018-08-13 00:37:28 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A24.922850875%2B03%3A00": status 200, 242 bytes in 0.16 ms
2018-08-13 00:37:30 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A26.422975385%2B03%3A00": status 200, 241 bytes in 0.17 ms
2018-08-13 00:37:32 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A28.457521416%2B03%3A00": status 200, 240 bytes in 0.17 ms
2018-08-13 00:37:34 http: GET "/rest/system/status": status 200, 1242 bytes in 0.41 ms
2018-08-13 00:37:34 http: GET "/rest/system/discovery": status 200, 3 bytes in 0.13 ms
2018-08-13 00:37:34 http: GET "/rest/system/error": status 200, 21 bytes in 0.14 ms
2018-08-13 00:37:34 http: GET "/rest/system/connections": status 200, 806 bytes in 0.29 ms
2018-08-13 00:37:34 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A30.49304165%2B03%3A00": status 200, 929 bytes in 0.21 ms
2018-08-13 00:37:34 http: GET "/rest/system/status": status 200, 1242 bytes in 0.38 ms
2018-08-13 00:37:34 http: GET "/rest/system/discovery": status 200, 3 bytes in 0.09 ms
2018-08-13 00:37:34 http: GET "/rest/system/connections": status 200, 805 bytes in 0.27 ms
2018-08-13 00:37:34 http: GET "/rest/system/error": status 200, 21 bytes in 0.08 ms
2018-08-13 00:37:36 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A34.361226517%2B03%3A00": status 200, 928 bytes in 0.21 ms
2018-08-13 00:37:36 recv 69 bytes from [fe80::d204:1ff:fe3c:bf4c%eth1]:37875
2018-08-13 00:37:36 discover: Received local announcement from [fe80::d204:1ff:fe3c:bf4c%eth1]:37875 for ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX
2018-08-13 00:37:36 discover: Registering addresses for ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX
2018-08-13 00:37:36 discover: Reconstructed URL is &url.URL{Scheme:"tcp", Opaque:"", User:(*url.Userinfo)(nil), Host:"[fe80::d204:1ff:fe3c:bf4c%eth1]:22000", Path:"", RawPath:"", ForceQuery:false, RawQuery:"", Fragment:""}
2018-08-13 00:37:36 discover: Replaced address 0.0.0.0 in tcp://0.0.0.0:22000 to get tcp://[fe80::d204:1ff:fe3c:bf4c%25eth1]:22000
2018-08-13 00:37:36 log 81 DeviceDiscovered map[device:ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX addrs:[tcp://[fe80::d204:1ff:fe3c:bf4c%25eth1]:22000]]
2018-08-13 00:37:36 http: GET "/rest/events?since=80": status 200, 313 bytes in 11967.66 ms
2018-08-13 00:37:36 http: GET "/rest/events?since=80": status 200, 313 bytes in 11941.43 ms
2018-08-13 00:37:36 write udp [::]:47925->[ff12::8384]:21027: sendmsg: network is unreachable on write to [ff12::8384]:21027 lo
2018-08-13 00:37:36 write udp [::]:47925->[ff12::8384]:21027: sendmsg: network is unreachable on write to [ff12::8384]:21027 sit0
2018-08-13 00:37:36 write udp [::]:47925->[ff12::8384]:21027: sendmsg: network is unreachable on write to [ff12::8384]:21027 eth0
2018-08-13 00:37:36 sent 281 bytes to [ff12::8384]:21027 on eth1
2018-08-13 00:37:36 sent 281 bytes to [ff12::8384]:21027 on docker0
2018-08-13 00:37:36 recv 281 bytes from [fe80::211:32ff:fe41:f1cc%eth1]:47925
2018-08-13 00:37:36 sent 281 bytes to [ff12::8384]:21027 on docker7389c40
2018-08-13 00:37:36 recv 281 bytes from [fe80::42:eff:fe6f:64de%docker0]:47925
2018-08-13 00:37:36 recv 281 bytes from [fe80::4843:9dff:fe89:f98d%docker7389c40]:47925
2018-08-13 00:37:36 recv 281 bytes from [fe80::b4b6:aeff:fed0:c02d%docker40ddb22]:47925
2018-08-13 00:37:36 sent 281 bytes to [ff12::8384]:21027 on docker40ddb22
2018-08-13 00:37:36 discover: Received local announcement from [fe80::211:32ff:fe41:f1cc%eth1]:47925 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:36 discover: Received local announcement from [fe80::42:eff:fe6f:64de%docker0]:47925 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:36 discover: Received local announcement from [fe80::4843:9dff:fe89:f98d%docker7389c40]:47925 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:36 discover: Received local announcement from [fe80::b4b6:aeff:fed0:c02d%docker40ddb22]:47925 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:36 recv 69 bytes from 192.168.10.195:40441
2018-08-13 00:37:36 discover: Received local announcement from 192.168.10.195:40441 for ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX
2018-08-13 00:37:36 discover: Registering addresses for ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX
2018-08-13 00:37:36 discover: Reconstructed URL is &url.URL{Scheme:"tcp", Opaque:"", User:(*url.Userinfo)(nil), Host:"192.168.10.195:22000", Path:"", RawPath:"", ForceQuery:false, RawQuery:"", Fragment:""}
2018-08-13 00:37:36 discover: Replaced address 0.0.0.0 in tcp://0.0.0.0:22000 to get tcp://192.168.10.195:22000
2018-08-13 00:37:36 log 82 DeviceDiscovered map[device:ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX addrs:[tcp://192.168.10.195:22000]]
2018-08-13 00:37:36 addresses: [1.2.3.255 192.168.10.255 172.17.255.255]
2018-08-13 00:37:36 sent 281 bytes to 1.2.3.255:21027
2018-08-13 00:37:36 recv 281 bytes from 1.2.3.1:37957
2018-08-13 00:37:36 recv 281 bytes from 192.168.10.173:37957
2018-08-13 00:37:36 discover: Received local announcement from 1.2.3.1:37957 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:36 discover: Received local announcement from 192.168.10.173:37957 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:36 sent 281 bytes to 192.168.10.255:21027
2018-08-13 00:37:36 sent 281 bytes to 172.17.255.255:21027
2018-08-13 00:37:36 recv 281 bytes from 172.17.0.1:37957
2018-08-13 00:37:36 discover: Received local announcement from 172.17.0.1:37957 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:36 recv 69 bytes from [fe80::d204:1ff:fe3c:bf4c%eth1]:37875
2018-08-13 00:37:36 discover: Received local announcement from [fe80::d204:1ff:fe3c:bf4c%eth1]:37875 for ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX
2018-08-13 00:37:36 discover: Registering addresses for ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX
2018-08-13 00:37:36 discover: Reconstructed URL is &url.URL{Scheme:"tcp", Opaque:"", User:(*url.Userinfo)(nil), Host:"[fe80::d204:1ff:fe3c:bf4c%eth1]:22000", Path:"", RawPath:"", ForceQuery:false, RawQuery:"", Fragment:""}
2018-08-13 00:37:36 discover: Replaced address 0.0.0.0 in tcp://0.0.0.0:22000 to get tcp://[fe80::d204:1ff:fe3c:bf4c%25eth1]:22000
2018-08-13 00:37:36 recv 69 bytes from 192.168.10.195:40441
2018-08-13 00:37:36 discover: Received local announcement from 192.168.10.195:40441 for ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX
2018-08-13 00:37:36 discover: Registering addresses for ST4MNKR-ZVPEUOA-55OEXCJ-WJ2EIYX-WVNFC57-6DQIUGU-F5ELASQ-UUBIRQX
2018-08-13 00:37:36 discover: Reconstructed URL is &url.URL{Scheme:"tcp", Opaque:"", User:(*url.Userinfo)(nil), Host:"192.168.10.195:22000", Path:"", RawPath:"", ForceQuery:false, RawQuery:"", Fragment:""}
2018-08-13 00:37:36 discover: Replaced address 0.0.0.0 in tcp://0.0.0.0:22000 to get tcp://192.168.10.195:22000
2018-08-13 00:37:36 http: GET "/rest/events?since=81": status 200, 293 bytes in 0.22 ms
2018-08-13 00:37:36 http: GET "/rest/events?since=81": status 200, 293 bytes in 0.20 ms
2018-08-13 00:37:38 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A34.671439494%2B03%3A00": status 200, 10559 bytes in 0.84 ms
2018-08-13 00:37:40 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A36.933273248%2B03%3A00": status 200, 243 bytes in 0.15 ms
2018-08-13 00:37:42 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A38.643943432%2B03%3A00": status 200, 241 bytes in 0.15 ms
2018-08-13 00:37:44 http: GET "/rest/system/status": status 200, 1242 bytes in 0.40 ms
2018-08-13 00:37:44 http: GET "/rest/system/discovery": status 200, 194 bytes in 0.17 ms
2018-08-13 00:37:44 http: GET "/rest/system/connections": status 200, 806 bytes in 0.36 ms
2018-08-13 00:37:44 http: GET "/rest/system/error": status 200, 21 bytes in 0.11 ms
2018-08-13 00:37:44 http: GET "/rest/system/status": status 200, 1242 bytes in 0.39 ms
2018-08-13 00:37:44 http: GET "/rest/system/discovery": status 200, 194 bytes in 0.13 ms
2018-08-13 00:37:44 http: GET "/rest/system/error": status 200, 21 bytes in 0.12 ms
2018-08-13 00:37:44 http: GET "/rest/system/connections": status 200, 805 bytes in 0.26 ms
2018-08-13 00:37:44 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A40.679878869%2B03%3A00": status 200, 1623 bytes in 0.25 ms
2018-08-13 00:37:46 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A44.675381286%2B03%3A00": status 200, 241 bytes in 0.15 ms
2018-08-13 00:37:48 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A44.73296845%2B03%3A00": status 200, 241 bytes in 0.15 ms
2018-08-13 00:37:50 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A46.782850846%2B03%3A00": status 200, 240 bytes in 0.15 ms
2018-08-13 00:37:52 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A48.810402743%2B03%3A00": status 200, 241 bytes in 0.16 ms
2018-08-13 00:37:54 http: GET "/rest/system/status": status 200, 1242 bytes in 0.39 ms
2018-08-13 00:37:54 http: GET "/rest/system/discovery": status 200, 194 bytes in 0.16 ms
2018-08-13 00:37:54 http: GET "/rest/system/connections": status 200, 806 bytes in 0.27 ms
2018-08-13 00:37:54 http: GET "/rest/system/error": status 200, 21 bytes in 0.11 ms
2018-08-13 00:37:54 http: GET "/rest/system/status": status 200, 1242 bytes in 0.43 ms
2018-08-13 00:37:54 http: GET "/rest/system/discovery": status 200, 194 bytes in 0.12 ms
2018-08-13 00:37:54 http: GET "/rest/system/connections": status 200, 806 bytes in 0.28 ms
2018-08-13 00:37:54 http: GET "/rest/system/error": status 200, 21 bytes in 0.09 ms
2018-08-13 00:37:54 write udp [::]:47925->[ff12::8384]:21027: sendmsg: network is unreachable on write to [ff12::8384]:21027 lo
2018-08-13 00:37:54 write udp [::]:47925->[ff12::8384]:21027: sendmsg: network is unreachable on write to [ff12::8384]:21027 sit0
2018-08-13 00:37:54 write udp [::]:47925->[ff12::8384]:21027: sendmsg: network is unreachable on write to [ff12::8384]:21027 eth0
2018-08-13 00:37:54 addresses: [1.2.3.255 192.168.10.255 172.17.255.255]
2018-08-13 00:37:54 sent 281 bytes to [ff12::8384]:21027 on eth1
2018-08-13 00:37:54 recv 281 bytes from 1.2.3.1:37957
2018-08-13 00:37:54 sent 281 bytes to [ff12::8384]:21027 on docker0
2018-08-13 00:37:54 sent 281 bytes to [ff12::8384]:21027 on docker7389c40
2018-08-13 00:37:54 sent 281 bytes to [ff12::8384]:21027 on docker40ddb22
2018-08-13 00:37:54 discover: Received local announcement from 1.2.3.1:37957 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:54 recv 281 bytes from [fe80::211:32ff:fe41:f1cc%eth1]:47925
2018-08-13 00:37:54 recv 281 bytes from [fe80::42:eff:fe6f:64de%docker0]:47925
2018-08-13 00:37:54 recv 281 bytes from [fe80::4843:9dff:fe89:f98d%docker7389c40]:47925
2018-08-13 00:37:54 sent 281 bytes to 1.2.3.255:21027
2018-08-13 00:37:54 sent 281 bytes to 192.168.10.255:21027
2018-08-13 00:37:54 discover: Received local announcement from [fe80::211:32ff:fe41:f1cc%eth1]:47925 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:54 discover: Received local announcement from [fe80::42:eff:fe6f:64de%docker0]:47925 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:54 discover: Received local announcement from [fe80::4843:9dff:fe89:f98d%docker7389c40]:47925 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:54 recv 281 bytes from 192.168.10.173:37957
2018-08-13 00:37:54 recv 281 bytes from 172.17.0.1:37957
2018-08-13 00:37:54 recv 281 bytes from [fe80::b4b6:aeff:fed0:c02d%docker40ddb22]:47925
2018-08-13 00:37:54 discover: Received local announcement from [fe80::b4b6:aeff:fed0:c02d%docker40ddb22]:47925 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:54 discover: Received local announcement from 192.168.10.173:37957 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:54 discover: Received local announcement from 172.17.0.1:37957 for DOR3545-HAMAAQQ-IDVRPTK-2L2EAD6-ZAJK5KN-N2Z4QCG-7MR55O7-VFZEVAT
2018-08-13 00:37:54 sent 281 bytes to 172.17.255.255:21027
2018-08-13 00:37:54 http: GET "/rest/system/log?since=2018-08-13T00%3A37%3A50.842620783%2B03%3A00": status 200, 6270 bytes in 0.66 ms
Edit: Post formatting