So I was out last night, and recorded the soundcheck... hit stop, the hourglass spun for a little while then the MT2496 froze.
This has happened once to me before, in the 2 or so years I've had the device. The previous time, I had no idea what to do and so wasn't able to restart recording for the main act.
So I searched a bit on here, and it appears that the magic sauce is to press and hold the power button for 10 seconds to force a hard reset. Needless to say, I wasn't able to reproduce the problem to test this... until last night.
So, to whoever wrote that advice,
, worked a charm! Got the soundcheck and main set, didn't miss a beat!
Hopefully by bumping this info I will save someone else some pain...