Hi Julie,
I had the same issue, yes you are right. It is the rear vent inside the boot is causing the issue. Either you can replace them. I bought a silicon sealant and pasted around the vent. Now there is no water ingress on my boot.
Another potential issue will pop up is Central Junction Box where all the fuses are there.. The box might have moisture will cause auto start stop failure, GPS failure.
Another potential problem is boot loom wire. Which causes your rear camera to showing cracked signals. Sometimes your boot might not open on pressing the button. But it can be accessed by remote.
