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. This is why I have a field in my database to record the battery replacement date of my customers. But it's definitely worth it. The key action feels like new, and it's operation is much quieter.
Organs are more reliable now, due to technological advances.
Allen Organ Company has recently begun using optical key switching on their new Rennaissance Series to further enhance the organ's capabilities. Their mechanical key switches were already the most reliable on the market, with large metal parts and individual adjustment screws for contact gap. Now they employ reed switches and magnets , while retaining the adjustment capabilites. Unfortunately, contact corrosion and broken contact wires are a common maledy, especially as the organ ages. For many years, manufacturers have been using solid-state reed switches in pedal claviers and drawknobs.