Mystery leak by Window - advice please

We have a mystery leak on our 17 yr old Rapido pop top. Given enough rain, the inside of the front nearside corner gets soggy and there can even be water on the shelf. I've marked the area in red on the first photo.

The window was replaced by our dealer under guarantee, albeit reluctantly, when the original de-laminated within months of our buying. We used Eeco in Halifax.
The problem started after that. I've stopped trusting the dealer & we're out of guarantee period anyway, so our local engineer identified that the window rubber seal had a gap in it, and he replaced that. No difference.

We can't identify that the water's making anything wet inside, the floor seems firm, likewise the walls, so I suspect and hope it drains away into the gas locker, but am anxious to cure it.

Pause due to health problems over Summer while we just protected it with a caravan cover for a few months.

Now I've practically smothered the "shelf" round the roof outside, where the various seams and joins are, with Sikaflex 512. As a result it hasn't rained properly since then! But the constant drizzle this weekend has produced a slight sogginess in the J-cloth I keep in there as a tell-tale.

Now I'm wondering if the wet comes in round the screw at the end of the strip at the top of the window. Are there any other unseen holes usually involved in installing this hinge strip?

It seems to come in quite quickly, and is very localised.

If I keep the window closed, then unscrew this and stick some sealer in before re-inserting the screw, am I likely to cause any other problem?

Should I run a bead of sealer along the top of that grey strip all the way across?

Any other helpful suggestions?

 Many thanks.