To be honest, there’s not enough info known to make any kind of guess at all but are you absolutely, dead certain, without a doubt whatsoever, that this transmission has actually been replaced 3 times?
If the original transmission was trashed and IF the converter was not changed/cleaned and IF the cooling lines were not flushed out then it’s possible for a new transmission to become contaminated by debris.
You refer to “remove and replace” transmission. In mechanicspeak that is referred to as R & R and it does NOT necessarily mean the transmission was actually replaced; only that it was taken out and reinstalled. Any chance of misinterpretation here?
As far as I know transmissions do not get sent back to VWOA at all. That’s all handled on the dealership level.
VWOA is NOT going to replace transmissions every other month under warranty. The service rep is going to be heavily involved the first go around, much less the second and third.
As a first step I suggest you contact VWOA and ask them to verify whether what you’re being told by the dealer is true. Ask for warranty claim documentation to prove this.