Rog..how old is your Mini ?
I have a 1977 model and I was getting false triggers and the warblys. A friend who's far more electronical than I checked it out and ended up replacing some parts on the VCO board, and completely recalibrated everything.
You may want to check out Arch Sound, they have rebuild kits for keyboards. I replaced a couple 'J' wires and all the bushings..big difference in the keyboard action. And, they're reasonably priced, I think the Mini parts were about 45$ US.
As long as it's torn down for cleaning, it's only a little more work, but well worth it.
Gary