This is pure guesswork, and seems admittedly unlikely, particularly if this happens often; however, it is the only technical interpretation that immediately comes to mind.

depending on the actual shot (and whether it applies only to one particular shot, or lots of different ones), it could be something as simple as either the sound, or the picture (if this were a video shoot) 'saturating' — i.e. overloading — which would be a good enough reason for knowing immediately that you'd have to go for another take. If the scene involved shouting, for example, the sound might well get overloaded; or if the camera moved to reveal a bright sky, then the picture signal (assuming video) might be overloaded. But I would have hoped any such problems might have been solved before Take 5!!!

I know this is pretty much a long shot, but if nothing else pops up, it is certainly a pluasible expalantion to bear in mind (though I have absolutely no specific expereince of this term in FR to back up my idea!)