I’m also having problems with El Capitan 10.11.1, USB driver 1.9.6, CI1. When playing video, sometimes it will fast forward very fast and break. If I stop it and restart it fixes it for a while. I think the problem is related to 48 Khz vs 441.1 Khz audio. I have noticed that in Audio Midi Setup the output sample rate will switch to 44.1 if I open a project in GarageBand that uses 44.1. If I quit GarageBand and play a video with 48Khz audio the output sample rate does not switch to 48Khz.