Since you didn't mention coach make model or type of slide mechanism, kindo hard to say for sure, but.....
If you have hydralic operated slides, specifically HWH brand, it is likely happening because the solenoid valve that extends the slide is leaking by, ie not closing completely. Might want to get a spare valve and swap that one out. Might just be a piece of sediment keeping the valve from closing completely.
This was explained to me by the HWH technician as the cause of the same problem on my coach. The fix worked.
2007 Adventurer 38T w/
sway & trac bars, Koni FSDs and SafeT+
2006 Jeep Liberty toad