yes it's the seal leaking.

2 things to do.

Get some black window caulk from your FLAPS. Put it under the outside lip of
your seal all the way around. You can roll it out pretty thin, 2mm or so.
Second get some screen window beading and insert it into the former chrome
trim slit. Window should be sound a a pound then.

Cheers,
Mark
87 westie