Jussi didn't manage to compile r345 for some reason so I had r340 from him and r355 from Max to test.
One (reproducible) problem occurred when trying to flash both firmwares with my Delta8 PPM receiver attached.
I got an error that only went away after I unplugged the receiver. After successful flashing I could edit the values as usual, set the motor mix and radio and everything works like it should incl. the tare function.
This might be helpful to know for upcoming testers. So don't attach anything else than the serial when flashing the fw.
Dunno if this happens with Spektrum or other radios...
Norbert