I have a 3-track, 8 bar loop with 3 instruments (Superior Dummer, Loom, and Roland Concerto - however it doesn't matter which instruments they are). When I play back the loop various midi notes drop out from random tracks. This happens very often on different songs with different instruments. It's not an interface problem as far as I can tell since the audio never fully drops out. The CPU Performance bar stays fairly low so it doesn't seem to be a CPU issue either. I've tried the 'clear your settings' method and the problem still exists.
This is on a MacBook Pro running Studio One 188.8.131.52603.
I've included a link to an audio loop of the 8 bar loop 3 times to demonstrate the problem.