Sounds like you have a hydraulic leak. It's either in the ram or the hose leading to the valve, in which case you should probably be able to find the leaking fluid as it drips on the ground.
Or, there is a leak inside the valve controlling that jack, so that the fluid slowly leaks back into the fluid reservoir. There would be no external dripping in this case.
Adam and Sue, and a pack of little furballs
2007 Holiday Rambler Endeavor 40PDQ Limited Edition - Cummins ISL 400
2013 Ford F-150 FX4 toad - USGear Unified Tow Brake, Roadmaster Blackhawk II Tow bar, Blue Ox baseplate
Home base near Buffalo NY, often on the road to a dog show