Our kitchen window was broken and I replaced it with a new one. On removal I noticed that it may have been leaking a small amount. The factory seals them with a thin lightweight foam weatherstrip. I used butyl tape installing the replacement. I then removed the window you are talking about and found the same. I'd suggest removing it soon and use the butyl. Check for wall damage when it's out.
I got around to the other small window (which was fine) but sold the HTT before I could get to the sofa window.
2013 F-350 CC SB 2WD 6.7PS
2013 Eagle Premier 351 RLTS
-SOLD- 2012 X23B
-SOLD- 2003 Ford Expedition 5.4, Bilstein shocks