Ouch...
I have an app, but it's on windows that make heavy use of playmaker, and I haven't had any report. I have an update on this app planned for next week, I will publish and mac and see if it does it.
Indeed, if it turns out fsm is unresponsive, this would be a nasty issue.
do you have repro within the editor? I work on mac, never noticed that, tho not really letting Unity run the scene in the background... Will watch out for this indeed.
Is your fsm within a prefab or something?
bye,
Jean