To reproduce:
1) Open attached project and the scene in it
2) Play it
3) After a bit of time, stop it
4) Select 'Metronome' object and turn off and on its Play on Awake setting
5) Replay the scene

Crash! Sometimes it would crash without bugreporter with only "Unity has stopped working", sometimes it would be proper hardcrash

NOTE: Sometimes steps 2-5 need to be repeated a few times, but usually it would reproduce immediately. It's hard to tell what exactly causes this

Reproduced in 5.6.0b3, 5.6.0b1
Don't seem to be able to reproduce this in 5.5.0p4 after multiple attempts