Could be. Logical in the sense that its one of the components where EMI is a huge challenge, but conversely it would be pretty crazy if the onboard charger was the source because they put a lot of effort into EMI filtering in the onboard charger and the penthouse area of the car for this exact reason. OP has tested two cars, and neither are showing any faults. Then there's the distance and the fact the gates start to open - 40m ish??Once you go above 16 A, a second of the three on-board 16 A AC to DC converters needs to be used. The circuitry that is load-balancing the power between them must be causing interference that the gates don't like.
From what I understand, all three phases are shielded and go into the single onboard charger which is a sealed unit with a crap ton of EMI filters. Shielding on this is super important because of where it sits in the car so it would be a pretty big leak... or faulty onboard chargers on two different cars.
I wonder if OP has had a mobile phone on the wireless charging pad both times... *dons tinfoil*