My jacks level great and retract great. Then after a few hours they start sliding down until they come in contact with the ground. Hydraulic fluid is full. These are not spring jacks. After I retract the jacks and start driving I get the warning light and sound that they are down. But when I go outside and look it looks like they’ve come down slightly. But after a minute the light and sound go off. Any suggestions on how to fix this?