Leaking barn doors at high level

[Rroger_D]

Rear barn doors leak at the top. I've narrowed it down to the join between the horizontal seal attached to the roof and the door seal / channel with the funny-shaped triangular bit at the top. By trapping a piece of film into the join (see second pic), I have managed to finally stop the water ingress but obvs not an ideal solution. Do you think it would be the horizontal seal that needs replacing? Presumably it squashes flat over time or, the vertical door channel seal?
From what I can tell, by pouring water from a watering-can on to the roof with the door open, the water builds up in that triangular piece and then 'overflows' to the left side (right in the pic here) and then down inside. I'm happy to replace whatever's needed but I just can't seem to work out what may have worn and how different a replacement would be for it to fix the problem.
Any thoughts?

van seal2.JPG

van seal3.JPG

van seal1.JPG