This came in from a customer:

So I bought a RME babyface a few years ago and had issues of audio drop out and glitches which appears to be quite common problems on the forum. After years I finally resolved the issue. It was not a software issue or fault on RMEs part.  The problem was a dodgy application of thermal paste on my CPU which caused overheating, which would eventually cause audio drop outs when the CPU would try and reduce workload.  I am writing this as another friend has the same issue with his Retina MBP and I believe the same solution applies.  I would definitely recommend you keeping this solution in mind when clients have concerns over audio drop out, get them to check if their cpu is registering particularly high, and getting higher after extended use.