Driver's side. Belt was damp after this last night's downpour, not at the top but at the bottom where it's spooled when not in use.

There's a bit of blistering to the paint on the sill just in front of the driver's door. Could that be causing the problem, or could the blistering be caused by wet getting in there from above?

Anyway.. Any ideas?

open the sliding door on the drivers side and look to see on the door there will be this bit that sits into a locating hole in the door jamb. that hole should have a plastic grommet kinda thing in it.. usually they get pushed in because the door over time shifts.
you can get them on Ebay but i would suggest getting your sliding door or the locating pin thing aligned again so it sits in the grommet and does not push it through into the pillar.

I'll have a look.