[schoir]

There is a small white plastic cup shaped like a small funnel directly under the drain hole and the foam liner.

Sometimes that cup/funnel gets separated from the drain tube, and sometimes the cup/funnel develops a hairline crack due to age and vibration.

In either case, it will cause a leak into the cabin.

In order to properly seal it, you have to remove the foam drain tray liner.

You can remove the foam liner only after removing the top frame assembly. If you look at the other parts of the DIY from where you got the photo that you posted, you will find instructions on how to remove the complete top and frame assembly. It's not overly complicated as it basically involves removing three 13mm bolts from each side of the frame base.

Regards, Maurice.