Intermittent Connection Error Messages

rei-zero246 · November 5, 2025, 2:56pm

Dear friends,

Recently, I have been encountering intermittent “Connection Error” messages.

Linux Mint 22.2 Syncthing v2.0.11, Linux (64-bit Intel/AMD) syncthing_log (574 Bytes)

marbens · November 5, 2025, 4:24pm

The warning message in the log you provided can generally be ignored.

Do note that the v2 WARNING log level is less severe than the v1 WARNING log level.

From the 2.0 release notes:

rei-zero246 · November 5, 2025, 7:11pm

Problem solved. While connected to ProtonVPN all of a sudden, I am losing packets and this acts like a disconnection.

marbens · November 5, 2025, 7:50pm

Great! I still don’t think the errors you cherrypicked from the log were the cause of your devices not connecting though.

100.85.0.1 is the default gateway and destination address on the proton-vpn-network-manager killswitch interface, so it is expected that you get that error if you have the killswitch enabled.

I think ProtonVPN caused both caused the error messages (expected, unless you’re running a NAT-PMP server on localhost), and caused your devices to not connect (unexpected).

Source:

github.com/ProtonVPN/python-proton-vpn-network-manager

proton/vpn/backend/linux/networkmanager/killswitch/default/killswitch_connection_handler.py

f85005cb0


      
              )
          
          @staticmethod
          def _get_ipv4_ks_settings(server_ip: str = None):
              if server_ip:
                  # accept/block all routes except the server IP route.
                  routes = list(build_routes_list(server_ip))
                  gateway = None
              else:
                  routes = []  # accept/block all routes.
                  gateway = "100.85.0.1"
          
              return KillSwitchIPConfig(
                  addresses=["100.85.0.1/24"],
                  dns=["0.0.0.0"],  # nosec hardcoded_bind_all_interfaces
                  dns_priority=-1400,
                  gateway=gateway,
                  ignore_auto_dns=True,
                  route_metric=98,
                  routes=routes
              )

rei-zero246 · November 6, 2025, 1:20pm

Thanks @marbens. The devices still connect/sync just fine; however, it was the intermittent “Connection Error” that was bugging me every minute and then it disappeared. I am using a router with OpenWRT installed. What do you recommend that I do, exactly?

marbens · November 6, 2025, 1:35pm

If ignoring the warning is hard for some reason, you can try reducing the log level of the nat package to ERROR (e.g. by setting the STTRACE environment variable to nat:ERROR).

rei-zero246 · November 6, 2025, 1:54pm

Thanks @marbens . The log warnings aren’t the concern, it is seeing the error show up on the GUI and refreshing the dashboard after every “connection error” warning.

I just stopped the VPN and I am still receiving the “Connection Error” warning. I am not sure what is going on, now.

marbens · November 6, 2025, 1:55pm

Is this what you were seeing?

This is a different error than the one in the log.

rei-zero246 · November 6, 2025, 1:59pm

Yes, that is correct.

marbens · November 6, 2025, 2:00pm

What URL are you using to access the GUI?

rei-zero246 · November 6, 2025, 2:01pm

https://127.0.0.1:8384/

rei-zero246 · November 6, 2025, 2:06pm

— 1.1.1.1 ping statistics — 300 packets transmitted, 300 received, 0% packet loss, time 299363ms rtt min/avg/max/mdev = 26.845/42.567/166.382/18.898 ms

— 127.0.0.1 ping statistics — 300 packets transmitted, 300 received, 0% packet loss, time 306109ms rtt min/avg/max/mdev = 0.021/0.067/0.224/0.012 ms

rei-zero246 · November 15, 2025, 8:18am

Is there a way, in the app, to capture why this is happening?

calmh · November 15, 2025, 8:31am

Check browser console for network or JavaScript errors, see what it says.

rei-zero246 · November 15, 2025, 8:38am

Is this outside of the logs on the GUI?

marbens · November 15, 2025, 1:44pm

Yes. I’m pretty sure he’s talking about the JavaScript console you can open with Ctrl+Shift+J on Chromium-based browsers, and Ctrl+Shift+K on Firefox-based browsers.