Arduino with RFLink via USB lets HA hang on startup

I have a Pi with a Adruino with RFLink connected via USB. When the HA has to restart its OS (not with HA Core restart) or a hard reset, the HA won’t start. When unplugging the USB and attaching it after startup there is no problem.

I cannot reach it via Putty, probably because its disabled anywhay and the logs don’t give a clue.

Does anyone have a clue?