We've been using a Fireface UC in the studio for 4 years now. It suddenly became inoperational 2 years ago and got RMA'd by Thomann (Germany). I'm not sure when it exactly started, but from some point on after the RMA, the Interface started exhibiting some odd behaviour.
The problem is, that it seems to lose connection to the PC for a brief moment, when a switch (on the same breaker?) is flipped. It often happens that, when I have music playing on the PC, I walk into the storage room to retrieve a mic or something, I'd then hear the music stop playing when I switch on (sometimes off) the lights. When that happens I need to restart the software (for example VLC, Firefox or Spotify) for it to work again. Cubase sometimes stops recording, showing the error message “Recording error: Audio dropout detected”, but I'm not 100% sure if that's the same problem.
My guess is that this is due to AC spikes, which I could filter out with a UPS, but I don't think this is normal behaviour, as this never happened before the RMA and also never happened with any other Audio Interface I owned, so I'd like to know what might cause this and if I could possibly fix this myself.
Today it "disconnected" upon switching on a power strip, which had a headphone amplifier connected to it. This never happened before, as I am aware of.