I have a Boss ME-6 guitar effects pedal. I got it around 16 years ago, it's been sat idle in the garage for quite a while now. Last time I tried it most of the buttons had stopped responding, so the unit was stuck with just the factor defaults. I'd feared I'd need to dust off my soldering skills to replace the buttons - although I'd not located exact replacements. However, as a last ditch attempt to get it working again, I dowsed the the buttons with WD40 wriggled them around and put it together again.
Rather surprisingly the buttons started working again, after a bit more exercise they were all back to normal.