Rear left trunk quarter, what the heck I'd leaking...

[Bmwe5320023.0]

The image shows the path of the leak as far as I can see it, if I lay in the trunk and get my head in there.
This is driving me nuts, there's nothing to leak up there. These small drops accumulate and flood my amplifiers, causing lots of damage. I decided to finally get to the bottom of it and won't stop until I figure out what's leaking...
The quality is not the best, but I showed with the red line where the leak is, and on another picture circles a little water drop that has just formed.
Did anyone ever have a leak from that area?? Read countless threads, there's leaks from blocked drains, from tail lights, from water in the tailgate etc., but never seen leaking from above there....

[Clavurion]

Could the source be trunk lid stopper on the side groove?

[EODguy]

Or coming in through the taillight gasket and running the edge till it drips?

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[Bmwe5320023.0]

Definitely cannot be the stopper, the stopper is waaay to the left and below the leak. Also with pouring rain, checked on the other side of the stopper, bone dry.
The tail light is way below the leak, and a lot to the side. Inalso sealed the tail light with silicone to completely take it out of equation.
The only thing I can think of right now is possibly damaged rear drain hose. Maybe water is escaping from there, and running down the D pillar or something. Cannot possible see what else it could be.
Two years ago I redid my headliner, and zip tied the drain hoses, so I can't see them coming off loose either.
I'll have to pour some water and try to do more testing. This is weird