The front passenger slide out in my 06 HR Imperial slowly creeps back in about 6" in roughly the same number of hours. I believe there should be a check valve in the hydraulic lines that prevents back...
Usually, Hyd Slide creep is caused by 1 or 2 solenoids leaking internally. You have a extend and a Retract solenoid. EITHER leaking internally can cause slide creep. This is assuming you have NO external leaks on to the ground. Hyd Slide rooms have continual pressure when extended and retracted. IF the system is allowing fluid to flow, then the slide creeps. Do you know what brand slide system? Usually HR used HWH IF they used the HWH Jack system also. Doug