MacBook Pro M1 MAX - MainStage playback fails due to CPU spikes

Hello!

This has been frustrating me to no end for weeks! I purchased a brand new M1 MAX 32GB to replace outdated MacBook for music production - Logic Pro and MainStage. I was using MainStage for playback of up to 8 backing tracks during live gigs. No plugins, no effects, no Aux sends - just .aiff files thru playback plugins into a Klark Teknik DN9630 interface to send multiple tracks to a Midas M32. This worked flawlessly on my old M1.

During rehearsal with my band, playback began randomly stop mid-song. Sometimes right at the beginning of the track, sometimes during a louder section. After trying everything I could think of - increased buffer size to 1024, reinstalled MainStage, created a brand new .concert from scratch, deleted the plist (MainStage settings in library folder), turned off wifi, etc. CPU kept spiking, randomly, to 300% or more, and playback ceased.

Finally, against all sense, I reduced the # of CPUs in MainStage settings from 8 to 4, then to 2, and lo and behold the CPU spikes are gone (so far) and everything is working as it should.

I can't imagine why on such a powerful MacBook with all that horsepower, I would need to *reduce* the number of CPUs in order to have MainStage work smoothly. Makes me feel like I wasted my money on something that could have been well handled at a far lower price.

Anyway, just wondering if anyone else has had this problem and/or might have some insight into this seemingly paradoxical bad behavior from these 2 Apple products working together.

Thanks!