A while ago I had a complaint about a recording I'd made. The (quite young) listener found it very unpleasant in places. On examination, I found from time to time, there was a quite high amplitude spike around 18-19kHz. My hearing fades out around 16kHz these days so I couldn't hear a thing, but I could certainly see it. A not too steep notch filter solved the problem, although of course I couldn't hear any difference.
The upshot is that these days I always have a quick squint at recordings before sending them out in the wild.
It wasn't me!
(Well, actually, it probably was)