If you mean that the slide is starting to extend while you are travelling is it happening on one side of the slide or both?
You may want to try timing the slide to see if that will correct the problem. If not you may have a motor brake that is getting weak and needs replacement.
I hate to say it but that is something you may want to have the dealer look at.
will come out about 1/2" on front side, even with it run in you can stick your finger between slide and wall. how do you time, you have my curiosity up. thanks blr