One more thing: check the connections where the pot is soldered to the board. You may have a hairline crack, or perhaps the solder connection did not "wet" the surfaces at original assembly, so that the very minor physical vibration of touching it with the screwdriver is causing an intermittent connection.
I don't know what kind of pots were used on that board. I would be surprised if the DeOxit® products would do them any harm. However if you wish to be 100% safe, do as recommended by "j beede". With the amplifier turned OFF, sweep the bias adjust pots from one end to the other a couple of dozen times and see if that makes any difference when you try to bias the amp again. This is likely to clean up any deposits on the resistance element or corrosion on the wiper.
Do not worry about "wearing out" the pot. If that's enough to wear it out, you needed a new one anyway and the manufacturer needs to take a careful look at the materials and workmanship they used when making it.