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.