If you don't notice any leaks coming from any of the hydraulic lines feeding any of the hydraulic jacks (stabilizers are a completely different technology usually found on trailers and are weaker devices that are not designed to completely lift a coach but only to stabilize), I mean, it is an older coach. The hydraulic lines may be cracking. But if not, then I'd suggest that you have a leaky valve block possibly allowing fluid to return to the reservoir. It could be crud that may be keeping a valve from completely seating.
- Or Air. You might have air in the system. I think there's a little bleeder valve on top of the hydraulic jack cylinders to bleed out any air in the lines. Cracking open that valve a little bit while the jack is deployed would then be the thing to do.
Hydraulic jacks are pretty straight forward: Pump - Valve - Jack. with hoses in between. Battery - toggle switch - valve / pump for the electrical. Over simplified, but that's the basis of it. your problem is not electrical. your just loosing fluid in the line, or there's air in there.
These suggestions might help you figure out what's going on.
