It happened on my 2017 T6, on the drivers door side seal. The seal gets trodden on when entering/exiting the vehicle and the rubber splits exposing the metal, which then rusts as it's not galvanised. I had the 3 yr factory warranty extended to 5 years and it was covered and done under warranty. However, the all-in warranty specifically excludes seals.
Since the seal was replaced, it has been fine. However, I have had to get in and out of the van in a slightly unnatural way, so that I don't tread on the seal!