I see a lot of problems associated with corroded edge contacts . Power Supplies create the precise voltages necessary for the different electronic subsystems. Some cannot vary more than one-fourth of one volt without causing damage to sensitive electronic parts. Like oscillators, they drift, eventually creating confusing or intermittent problems. Also, power transistors and ICs, which generate heat during operation, will last longer when not coated with an insulating layer of dust.
Most organs employ a computer-type memory system to hold registrations.
Most of these systems require a backup battery to sustain the memory circuits in case of a power failure. Most battery packs last about ten years, some only three. You may think your battery is working fine, but it could be defective without showing immediate signs. If all registrations are lost after a short power outage, the battery pack is probably bad. I have seen some organs refuse to power up because the battery had shorted out.