I have one griddle sort of pan. Don't know its proper name. Don't remember
its brand either but it was fiercely expensive. The instructions that came
with it said: NO dishwasher and NO spray-on non-stick like Pam. I won't buy
another one of that ilk but have great happy results with it. So great that
I gave one to DDIL.
Hers did just what you said; worked fine and then it was awful. Be very
careful choosing non-stick cookware and really do follow the instructions.
Polly