Many of us have found out the hard way about these camper windows.
I had the rear kitchen area of my Bigfoot leak the day I bought it.
Instead of taking it back to the dealer 300 mi I elected to fix it myself and see why it would leak.
I removed the window using a heat gun and plastic putty knifes. Not too much heat just enough to soften the Butyl tape sealer.
I found that the window was not sealed at the right top side.... After I cleaned up the window and opening I placed the window up there and found that the curve of the camper corner starts where the window sits... Ugggg... It too 2 layers of Butyl tape to provide a proper seal.
I also found that it is imperative that the screws around the windows be repeatedly snugged slightly a few times. You want the sealer to ooze out... If you start to tighten the screws I would first check to see if some are not even tight! Snug those down slightly, then turn the screws maybe 1/4 turn each... You should see the sealer slightly ooze or bulge a bit.
I would wait 3-6 mos and do it again...
I did all my windows after finding out that the windows were not sealed properly. After about 3 years I removed the excess oozed sealer...
If your camper is old you may need to remove the windows that do not ooze sealer and re-do.
There are a few examples of what I have described on our TC forum...
Jim