[1] Are you using:
a) a dedicated audio interface or
b) a built-in sound card?
If a) is it USB or Thunderbolt?
[2] Additionally, do you have any sleep or hybrid sleep features enabled?
[3] Review also your power options. Useful article: [blog] Optimize your Mac for a gig
[4] Next step: does this happen when you try built-in templates in Gig Performer?