I have the following. 2002 Gulf stream Conquest. It has two slides and the problem is... The rear slide continually creeps out. It is a hydraulic piston slide system No leaks ,fluid is full ect. The ...
Take the cylinder out and have it rebuilt by a hydraulic shop. That would by my first step. If that does not fix the problem, then go to the valve and replace it. Not uncommon for valve seals to leak, so if your really handy taking it apart and changing the "O" rings could cure the problem.