Wasted an hour or two on that...
After changing the library I used, was trying to test that my Java WebSocket client was reconnecting as I intended upon losing connection.
Me : Why are you making the rest of the app bug you stupid fucker? The old one was doing fine!
WS : ...
Changes code, looks on SO a bit.. Gets despaired.

Then it struck..
The "rest of the app" was connected to a sensor.. On the network.. From which I disconnected to mimic a loss of connection...
😭😢😂😂😂👌