HELP NEEDED - Leak seatbelt

I have a 2014 runner sr5 with third row seating, on the drivers side rear seats (not third row but middle seats) there is a leak coming in from the seat belt. I have removed the roof rack and sealed the roof rack with rtv black and it still leaks. I put it around everything to ensure it was sealed. The sunroof doesn't seam to have any obstructions in the drain holes.

I have exhausted all ideas, what could be causing this?

 

Dumb question, but has anything even remotely-related could have happened that could have started it? Window replacement?

I'd look at pulling the headliner, see if you can trace the water stain somewhere or if it's spotless, maybe the leak originated below it?

Run your hand all over the headliner before you pull anything, maybe the leak is elsewhere and simply shows up on the C pillar first.

 

No window replacement or anything that would've caused this.

 

Check the door seal, see if it's worn out or damaged at all. I bet it isn't creating a tight seal.

 

Take a garden hose and check suspect areas (sunroof, door seals, roof rack base)

 

This^
Dry the area inside and then either spray water or use a garden hose from the outside to see if the weather stripping, door sear or even the window is cut,lose, misaligned.

 

Maybe a sprite?