Last night (2020-07-13), a rule action changed the mode to Theater, but another rule whose only trigger is "Mode becomes Theater" did not trigger.
System events show the mode change, which was expected based on my rules:
There were no other mode changes soon before or after this. This should have triggered the following rule:
Those actions didn't get executed, and the log shows that the rule didn't get triggered, despite having trigger logging enabled:
Interestingly, the logs show that the separate "Init mode / Sleeping" did pick up on the mode change, even though it correctly didn't trigger that rule. So at least one registered mode trigger worked, but at least one was dropped.
The "Init mode / Theater" rule's events confirm it was not triggered (the later 10:38pm trigger is unrelated, due to entering Theater mode a later time, which worked without issue):
None of the related rules has changed in weeks. Maybe relevant: I had rebooted the Hubitat ~10 hours prior, which was after the previous time it had entered Theater mode.
I'm on v184.108.40.206.