Capillery water leak under flashing on 3" profile garag

Not quite sure how to fix this one, maybe expanding foam? though I wouldnt want the foam pushing the roof up if thats a possibility.

The garage is attached to the outside rendered wall of the house. There is alloy profiled flashing over 3" clear plastic panels. This leak is quite a way in from either end so getting up there is not really an option as the panels are quite old and brittle, I bet they will crack even with a crawl board.

The rain is being pushed by wind back up the panels under the flashing, once it gets going there seems to be capillery action to keep the flow going. Its only a small 50cm section thats doing it so I guess the flashing must be slightly high there as durite chippings or moss has built up under it.

Here are some pics.

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I can't see how you hope to get a lasting fix by going from the inside, this would require attention from the outside.

If the sheets are as brittle as you say then it may be time for a re-roof maybe?

Well the sheets were put up after the hurricane of 87 and were 10yr warranty 1.1mm ones. I assumed they would be brittle after a firework rocket casing bombed through it a year ago.
The garage is 12mtr x 3mtr so an awful lot of sheets to replace should I go that route, I have elected to add more timber supports under the sheets and use 2" tube laid along the valleys of the sheets bearing on as many timbers as possible with scaffold boards on top to see if I can get to the mid position and do a repair from there.