Most epoxied pickups that stop working normally can't be fixed. It is difficult to remove the epoxy without breaking the coil or bobbins. You can't repair them properly and several pickup builders pour the epoxy directly on the fine magnet wire. When the epoxy dries, it can shrink and in time break the inner coil. We get many in for repair and most are not worth repairing. It's like buying a flashlight with only one bulb.
Some builders feel the epoxy will permeate the coils but typical epoxy solution is to thick so they need to insulate the coil better to avoid their pickups from breaking down the road. It's a drag too because you spend a lot of money for your pickups and they should work for the life of the instrument. Much of this can be avoided if they spend the extra time and money to wrap tape around the bobbins.
WRITTEN ON JUNE 12, 2015, BY