ᐅ Terrace Door Exterior Floor Waterproofing

Hello everyone,
I have a problem with my basement door, a floor-to-ceiling two-leaf door, and urgently need your help.
I noticed that water is slightly getting inside. I then removed the paving on the outside and found that the PCI Thene membrane I installed had come loose. As a result, water gets underneath the black foam seal under the window, exactly at the corner, and travels inside.

I tested this with water from outside, so it’s confirmed.
The drainage is located directly in front of the foundation slab.

Now to my question for the experts:
My idea is to straighten the side wall connection, neatly cut off the existing PCI Thene, and then properly overlap and stick it back on with PCI Thene. Would this approach be okay?

Or should I install a PCI inside corner piece in that corner?
PCI BT 45 inside corner
Art. No.: 005020011235
PVC fitting
Sealing of foundation corners
Should I place this still in the corner?

I would really appreciate any advice you can give me.

Thank you in advance and best regards,
Oliver