Condensation on inside rear windscreen

[Porsche996fan]

I have a 2015 991.1 C2 with factory fitted Aerokit ducktail spoiler. After heavy rain today and then about a 90 min drive I noticed condensation on the inside of my rear windscreen. The fabric lining the parcel shelf under the rear windscreen is damp, more so on the driver’s side, and it’s damp under the inner trim at the base of the rear windscreen. There’s also condensation inside the drivers side rear light cluster.
What’s the likely cause?

 

[595triple]

Without wishing to worry you unecessarily, the drains may be blocked and water is getting into the car. Drains are supposed to be checked during a service and cleaned. If they get blocked and overflow then the carpet can get wet and there are electronics under the seat, parcel shelf etc. The parcel shelf upholstery is easy to lift as its where the suspension control unit lives (if you have PASM). I would have a check in there for leaks. Check the carpet under the seats also.

If you want a copy of the 991.1 workshop manual to look for the drain entry and exit points PM me.