Slide out sliding out in tow

I had the same trouble. Had it fixed at Lippert while at a rally in August. It was an internal hydraulic leak in the ram. Also be careful about putting something between the frame work and the wall inside to try and keep it from creeping, I did that, it still crept out and pulled the framework off the slide about an inch before I caught it

My '98 5er came with a couple of shower curtain rods cut just slightly longer that the space between the wall and the slide lip. They have rubber tips and wedge in nicely.

Here is a bit of picture of what I use.

Most probably you have a blown seal in the hydraulic piston. Had to replace both in my 2002 Montana. If it doesn't ride out when parked, it will eventually. The fix is relatively simple if you are a DIY guy. I removed mine from the trailer (not fun having to remove the underbelly) and took mine to the local hydraulics shop and he replaced the seal, charged 25.00 for the first,
and 30.00 a year later for the second. Locks and latches may work, but not worth the hassle in my opinion, you still have to worry about it riding out enough for water to enter during a rainstorm.

When you find a cure be sure and post the results, it may help someone down the road.

Internal hydro leaks can also be inside the ram itself, with oil leaking past the piston seals.

Lyle

You have a leaking solenoid on that slide.
It is allowing hydraulic fluid to bleed off hydraulic ram which then allows slide to drift.

It will just get worse so have it fixed before you can no longer operate slide and it is stuck out.

You could also purchase a couple of slide out locking bars to hold it closed (OR make your own out of 1 1/4" wooden closet pole rod and rubber tips ----measure twice, cut tight allowing for thickness of rubber feet)

We had a 2010 Montana and inside the outside control panal where the switches for the front jacks and rear stabilizer were there were four shut off valves for the individual slides. When you closed them the slides stayed put

I heave a ratcheting expanding bar I use in my pickup bed to keep things from sliding forward. It's got nice wide rubber feet on each end to prevent surface damage. A couple of these would work perfect if you're looking at something until you get the motor thing figured out. Or, just as a safety in the future. I've heard these talked about as a safety thing before.

My 2013 had a bad solenoid on the bedroom slide that caused the kitchen slide to creep while driving. It took a FR tech to figure it out.

You have an inturnal leak, get fixed and all will be good.