I reported the following to NI tech support: I've been using Traktor for a very, very long time (see e.g. http://www.native-instruments.com/forum/threads/s8-initial-impressions-feature-requests.229461/) and last night I had an experience while playing out with my S4 and F1. The scenario went something like this: • Playing as usual • Load a track into a deck, overview waveform shows but detailed waveform does not (I'm not 100% sure this always preceded the problem, but it definitely did on some instances). • Within the next (roughly) 30-60 seconds, audio starts dropping out on other channels (e.g. remix deck, opposite track deck) until nothing at all will play through the S4 • Loading new tracks, turning off/on the S4 has no effect, restarting Traktor has no effect, only completely restarting computer will restore audio. I tried increasing the latency from a very low setting which I have used for years without problem and while this seemed to perhaps increase the duration between occurrences of the problem, it did not stop it from re-occuring multiple times over a five hour set. I have included several hang logs which may or may not have corresponded with the issue. This is a very, very serious stability issue which I haven't seen really ever in many, many years of using Traktor. Running Mac OS X 10.10.4, S4 MK2, 16 GB RAM, 2.6 Core i7. Never any issues on this machine for many, many years.