So I set up my live rig the other night, and I'd lost one channel :dunno: , in the light of day I worked out it was because both the input parallel and ground lift switches were "in", The ground lift wasn't an issue (although not required), but the input parallel switch (used for bridged (mono) mode turns off one channel (mostly, it's still there soft when you crank in stereo)). So it seems I've accidentally pushed the switches in when coiling the cables into the back of the 2RU rack case and closing the back (not always done completely sober BTW :facepalm: ).
Anyway, one to watch out for if you use a TS100 LOL, cost me a bit of trouble shooting to find.