I have a 2015 185RB Baja. I, too, have found water on the bed next to the front window but couldn't really find a source.
I thought about removing the front window but figured I'd try a couple of sealing steps before that.
The black window frame appears to be compressed against some type of rubber or foam seal. I silicone caulked over that rubber/foam seal between the black frame and the white siding. I left the bottom un-caulked on all of the other windows (for water drainage, should any get in and around the window for some reason), but I caulked all the way around the black frame on the front window. I have a thought that wind driven rain while driving might be sneaking up underneath the bottom edge of the frame.
I'm also replacing the rubber weatherstrip gasket around the glass. It has shrunk over the last 7 years and is loose in a few places.
I've had a very difficult time finding the same profile seal as the original weatherstripping; however, I got a short piece of a similar profile from the local RV dealer. It seems to fit perfectly in the frame (with a little soapy water to aid installation) and seems to be tighter than the original.
If those two steps don't work, I'll be coming back here to see if anyone else knows how to get the window out.