Mainstage 3 Crashes when left unattended

I'm running Mainstage 3.4.2 running on an iMac 2009 with 8G RAM and OS High Sierra 10.13.6

Everything works and sounds beautiful, except...

Whenever i leave my computer unattended for an extended period of time (it could be 30 minutes or overnight), Mainstage consistently crashes. When i try to return to my project, i get the spinning wheel of death, and have to force-quit Mainstage and relaunch my concert.

I have my energy saver settings all turned off. Memory and CPU indicators are nominal (ie., not overloaded).

Anyone have any ideas? I'm turning off my screen saver next to see if that could be the culprit.

Thanks.