On my 90 the water was coming in where the roof meets the window.
The rubber seal between the two started to develop gaps and was letting water through and onto the headlining where it stayed until i went round a corner.
I sealed it with some clear sealant, it doesn't look that pretty but i'm a lot dryer.
Next time it leaks look where the water is coming from.
Does it look like it's coming from above the door between headlining and body, if so it could be coming down from the headlining.
If the door was poorly fitted it would come past the seal and over the top the door and not from above it.
If there was a poor seal where the seal meets the body you would get a small amount coming through fairly consistently when it rains as opposed to what i had when nothing would come through for a while until i went round a bend and got a bit of a waterfall.