Just a note that when I run just the demo content, even in a single layer after about 20 sec the clip pauses and the FPS drops to 1-3fps, I get a beach ball and then it picks back up to 60fps.
Looking at CPU load it never goes over 10-20% most of the time - although CPU % varies from 53-124.9 in activity monitor, which should be fine for a multicore processor. That variation also doesn't seem to have any relation to the stalls in playback.
When I first spotted this bug the right click menu on a clip wouldn't go away and I ended up with multi ones - in that case Resolume wouldn't quit (the dialogue did pop up - but I couldn't click QUIT) so I had to force quit. You'll also spot that the clip in preview isn't the one that is selected to preview.
rMBP 2013 2.6 i7 w/ 750m 2GB, running 10.11.1.