It probably is a leaking solenoid, Cyril. You might get a lot of information from the thread, "Front Driver side slide-opens 1 inch on its own", that ran in this Forum starting in April of 2010.
http://forum.bacrallies.com/m-1270760875/s-0/ One of our slides started creeping out slightly while the coach was just parked in storage by our house a couple of years ago. Simply acivating the slideout out and in stopped the problem. HWH suggests holding the slideout switch for awhile after the slide is in to build system pressure that helps prevent the creeping you're experiencing; I would add to that good idea that holding the switch afterward for only a second, two at the outside, should be adequate, and is easier on seals and your pump motor. I think sometimes the solenoids' O-rings just need reseating for various reasons. Other times they may need replacing. But simply building pressure momentarily in the solenoid after the slide is closed may very well be all you need to do here.
Our slide solenoid manifold is located under the passenger front of the coach, near the entry step, if you still need to know where yours might be after trying my suggestion above
.
-Joel
