What year is your Montana?
If under warranty call Keystone ASAP!
Sounds like a seal is bad or had something damaged it. Open slide and inspect seals check when slide is open halfway from inside then outside.
Agree with above that water probably didn’t get in ceiling of slide.
Good Luck
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Wayne & Malinda
2018 Montana 3731FL
MORryde IS/DiscBrakes
2017 F450 DRW KR 4x4
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