Trimpot failure?

[mnordbye]

From time to time, after biasing a pedal using J201s etc., i find myself playing with it for some time when it's working like it should. But when i turn it on again next time i'm gonna play, it's unbiased. So then i have to open it up, thinking "ohh, what's wrong this time?!"  . But i've learned that the first thing to check is the trimpot. Then it has jumped to either a too high or too low voltage. All i have to do is turn it until it says 4,5 volts (in most cases) again.

I'm just wondering, have anybody experienced similar things when using trimpots?

[punkin]

I've found FETs that won't bias. Checked and checked but found nothing to fix or repair. Replaced the FET and bias set up as "by the book". It happens.