Conservatory box gutter leaking?

paperclap

Hi all,

Pretty tired of leaks at this “home”, but here we go again!

We’ve a leak (circled).

I’ve a suspicion the water is getting in on the far end of the box gutter (doesn’t look greatly sealed), running under the gutter (on top of the PVC), and finding the lowest point…

Any thoughts based on the photos?

Excuse the masking tape on the window. For what feels like forever, I’d been taping some old roof membrane to the window to redirect the water into a bucket below. Sad times.

paperclap

Bump! Anyone out there?!

ThisIsWeird

I'm not familiar with these types of gutters. Is that end 'cap' a separate part? If so, it's hard to tell how well-sealed it is, so is an obvious suspect.
Bear in mind that the water could be getting through pretty much anywhere along the gutter, and then travelling to that far end after having trickled along the top of the internal cladding before coming through in that corner.
Also, in that 4th pic, the slate overhang isn't great, so could coursing rain be blown in behind the gutter?
And what sort of join has been made between the two gutter sizes there?

It may be time to grip the issue, and begin by taking down the internal PVC cladding, so you can hopefully trace where the water is actually coming in?