Hi,I actually just had this same issue. It didn’t get all the way to the back seat being wet but the spare tire area was soaked. I tried the small drain tube behind the logo; cracked but not the issue. I bought new seals for the taillight; not the issue. I noticed it was more wet on the left side than the right so I started tearing things apart on that side of the car. Trunk carpet out and left hand trim in the hatch removed. From there, I could tell that water was collecting in a small little pocket and then sloshing over into the hatch tirewell area. The only open into that area was the pressure vent; the item in question. It is pn: 7N0819465E
It pushes open from one way to equalize cabin pressure and has a seal around it to prevent water from entering. I replaced it and silicon sealed it in place to prevent further issue. That was at the end of 2018 and I haven’t had water issues since.
Here is where it’s at in the parts diagram:
Here is a picture with the rear bumper off; notice the rectangular vent:
Just wondering where you bought the vents please ? Would you have any links..
Thanks,
Rob