i have gone through this recently
that is the result of many little things
first is the position of the door, probably too much opened at the front gap
then the triang window frame assembly, fix it with the door opening as close as possible to the front
then the new felt U channel, use a 5mm thick wood piece and hit it with a tubber hammer to place it as in as possible
and then the position of the glass relative to its fixing plate
i mean there is a rectangular steel plate that fixes the glass with three hexagonal bolts, that has a play because the holes in the glass are slightly larger than the fixing points, so if you loose the bolts, you will be able to move the glass forward a bit
i did all this and i can close the door maintainig a gap of 7 mm between the rear trim and the front window
regards