Late 90's Fender Hot Rod Deluxe.
It used to pop, crackle, spontaneously switch channels, buzz (completely interrupting notes) & fart in the bass notes. Playing G# would cause the amp to hum in G# or something like that- some kind of noise only when I played G# or something anywhere on the neck.
Brought it to an amp repair guy, whence it suddenly worked fine, & they couldn't find anything wrong with it. I brought it home, & it all started again.
When I moved I had it shipped to me, which cost me $90. I sold it for $150, & went back to using my old Super Reverb, which I have never had a single problem with.
The whole experience made me wary of owning any amp with printed circuit boards.