I got the same behavior with observer in edit mode. When using the property as an argument i have to save and close the editing window to have it working. So annoying !

Could you make the test with a message 'property is_playing' instead and see if it works ?

Hmmm so you tried and it wasn't obesvering at all in edit mode?

I think the problem i was witnessing before may have been that the gate was actually getting stuck CLOSED, but in any case i made the change and it doesn't seem to be behaving any differently. I haven't as of yet been able to recreate the issue i was seeing previously, but i have pinpointed a different quirk. It happens when the set is not playing and you close the editing view. Up til this point the gate will be closed as you'd expect, but then in performance mode the device will act like the gate is stuck OPEN, until you actually do start the set playing and then stop it, after which it will act normally. Thanks for the tip though; i'll have to continue to diagnose this thing and see what's its deal is.