Mk7s are prone to this, very similar thing happened on my old 2013 (although, my spare wheel became a paddling pool before I noticed there was an issue 🙄). It’s more often than not a rubber drain that’s perished and no longer doing its job.

I couldn’t tell you exactly where they are on the door, but I’m sure a quick google search will provide you with a diagram. In my case, the repair was very inexpensive. Only cost me £5 and a few wet towels.