Symptom: Boot filling with water. Traced to the seal between the rear panel & the internal shell, either the selant needs replacing or the drainage channel is blocked.
Removal of the rear wing is required to access this area.
Drainage You will notice a strip of mastik/gunge along the top, there is or should be a gap where the water is guided down an internal drain. If this area has been sealed at some stage, it is possible to block the drain and fll your boot.
Sealant Test by placing newspaper in the area of the boot where the water has been appearing, then slowly pour water in the channel between the rear panels and see where the drips appear, you may have to replace the sealant to fix the problem.