That warning light...
Warning: not a pilot, so probably about to use all the wrong terminology.
Passenger evidence suggest the pilot saw a warning light displayed, but wasn't sure what it meant.
Of course, it could be that the passenger didn't pick up the pilot's words accurately, but assuming that he did, is it usual for a warning light to be difficult for a pilot to interpret, ie needing an engineer's analysis? I imagine pilots get frequent warning lights, and I've always assumed they could make reasonable sense of them on the flightdeck. If they can't, does that suggest a problem that needs a bit of careful analysis by maintenance staff?
If it was a warning light, that would suggest that the relevant systems had detected something wrong. Would the activation of a probe heater normally set off a red light, or is the pilot simply 'notified' that the heater has switched itself on? Does it make sense for the probe heater to set off a warning light?
The heater deactivation seems to be about the only unchallenged fact we've been given so far, and something about it doesn't make sense to me. If the red warning light was a bit of a mystery, could it be that the 'solution' didn't fix the real problem?