389 sleeper leaking water

I would be getting to the first dealer ship of that truck cause that should be under warranty. If the leak gets any bigger, imagine coming up out of Hialeah,fl and it's raining so hard on the turnpike they have signs up that it's free, as a hurricane is coming in. Hopefully not in your case but everything_meaning yours_ gets drenched. The company prolly ain't gonna reimburse you for anything. To me that would be a #1 priority fix brother!

 

Gaskets can go bad yes. Easy fix, another place it leaks from is if you have a roof ferring is the gaskets around the mounts can go bad and water can leak in from those. Condensation especially if you use a Cpap can also build up on the cheap aluminium/mylar insulation they use and drip down. That one is solved with either leaving a window cracked or a dehumidifier.