My PI3 has been running syncthing happily on 14.17 during my three week absence overseas. On return, I upgraded to 14.19 and syncs with other machines (Ubuntu 16.10, amd64, syncthing 14.19) failed, or very slowly progressed, even with small files, never reaching 100%.
Return the PI3 to version 14.17 and all is as expected. I have not tried 14.18.
If needed, I can return to 14.19 and share logs, etc.
Depends on how you start syncthing. If you use a service manager, the config file for syncthing should point to a file where the stdout is redirected. If not, there is no log.
If you start it manually, you will have the log in your console.
I’m seeing a similar problem on a machine running Ubuntu 16.10, amd64, syncthing v0.14.19 “Dysprosium Dragonfly” (go1.8beta2 linux-amd64) jenkins@build.syncthing.net 2017-01-10 07:50:11 UTC