It wasn't somebody else's code, as I found out after inconveniencing several coworkers, finding out all files that have been recently updated and otherwise causing a great hubbub. It's a hardware failure. I'd have found out sooner but these are prototypes and there aren't many of them, and of course no two work quite the same...
But I may be done very, very shortly. I may be back to dealing with the amount of work that genuinely needs to be done.
I'm tired.