I have two musicians I've played with who have perfect pitch, and I've seen it fail for both. One is an older man, whose legendary perfect pitch started to fail in his early 60s (not much later came the onset of early dementia, so...).

The other is a bandmate of mine, a woman in her late 20s/early 30s when i saw hers fail. She's genetically predisposed - both her father and her brother have perfect pitch; plus her father is a professional musician, she has a degree in music performance, and has had a violin in her hand since she was old enough to hold one. One day, we were recording, with her overdubbing parts onto some previously recorded work. She complained that a B flat played at the start of a guitar riff was out of tune. I said "No, that's a B". She insisted it was a B flat. I told her I had also played the part on keyboards, and it's a B.

She panicked.

It was extremely difficult for her to play for the rest of the session. Her playing relies so heavily on her perfect pitch that she's always had, that when she can't trust it, anxiety takes over.