Nice that you got an expensive new charge port but clearly your car didn't need it. Sorry you've had to make so many trips to the dealer. The error code sounds to me like a bad connection or ground wire somewhere in your car. Maybe take a very close look at all of the electrical connections related to the on board charger? Do you see any connectors that look damaged or loose or see any ground (brown in color) wires that are not secure?
I would continue to complain to the regional VW manager. Does the dealer that serviced your car sell ID.4s? If not, maybe you need to take it to a dealer that does as I would hope an ID.4 dealer has technicians who are better trained than those at pure ICE sellers.