Unfortunately, it looks like what you have is the gasket "window-creep" problem common to many Bigfoot
models over a specific three year period, I think 2003-2005. We have the same problem in our 2003 25RQ. Attached is a photo of what one window looks like in ours. (Still not very good at attaching photos; hope it worked.)
We knew of the problem and tried for six months to find a used Bigfoot
avoiding those years. The trailers are so good and so hard to come by that we finally couldn't resist one that was in great shape, except for the gasket creep.
It's caused by to a defective gasket between the double panes of glass. I've spoken to Bigfoot about it and they are aware of the problem, but there is nothing they can do about it, especially since Bigfoot has reformed after going out of business for a couple of years around 2008.
Most people say the problem is mostly cosmetic, and not necessarily associated with leaks
. I've read on this site that the window fabricator knows about the defect, and some folks have gone to Canada and actually had the windows repaired by the fabricator at a "reasonable price"; not sure what that would be.
We just had a week of rain in Arizona and I have found some water in the inside slot for the slide-track of some of the windows. Because of the continuous rain, I haven't yet tried the first step of cleaning out the outside weep holes in the frames, to see if that helps.
On the more extreme side, I have ordered some Dicor non-sag sealant, and EZE RV & Marine window gutters suggested by other readers. I'll apply those when the materials arrive (and things dry out a bit). If all of that doesn't work, the last two options are to take the windows out and reseal them, and possibly replace the offending gaskets at the same time. Not quite ready to fact that yet.
I'll see if I can find one of the earlier conversations on this subject and pass it on.