Hi Paul,
The program (almost) always crashes immediately upon pressing a key on my MIDI controller (Kawai VPC), attached via MIDI cable (not USB) to a Focusrite Scarlett 18i8 (1st generation). Often not playing for a minute or more seems to trigger the crash: As soon as a key is pressed again, Synchron crashes. Other crashes are purely random and occur while playing.
I've sent crash reports every time for months, so you should have literally many hundreds of them by now!