Probably hydraulic pressure leaked (or drained) down on the "in" side of the actuator and the slight pressure on the "out" side of the actuator pushed the slide out slightly. Any loss of pressure on the actuator (if the trailer is sitting with the slide slightly tilted down or up) would cause the actuator to allow the slide to drift in the direction gravity is pulling it. I believe there is a locking mechanism on the actuators (to keep the slides in during travel) but if the pressure drops to zero, I don't know if the locks will still function. If they don't, then essentially your actuators are "free to drift" and the slide may creep open. It's "sort of" like the front end loader on my tractor. As long as there is pressure on the actuators, the bucket will stay up, but if I shut down the tractor, eventually the actuators will "leak down" and the bucket will start moving slowly toward the ground.
You could cut a couple of "2x4 wooden blocks" to wedge behind the slide facia and the outside wall as a means to keep the slide from drifting out when in storage. If you so, don't forget to remove them before powering up the system or you could have a slide that wants to move and a block that is in the way causing some "ugly damage"..... There are slide locks available from most RV parts stores, but they are designed more for travel and you shouldn't need anything that elaborate.
http://www.factoryrvsurplus.com/prod...product_id=495
Linear Mode
