You do wonder if you car drive through it then! - sounds like the 2 motors / drive trains are syncing at a certain speed / frequency (1st harmonic) - Im sure they have tried to resolve it with software (or maybe not given their track record on LKA

).
In my view, we are producing too many software engineers and not enough traditional mechanical engineers.
If it as a software issue, it would be a "feature", not a "characteristic" .....
Maybe more an issue with robot calibration, more than one line of robots welding up particular suspension and engine mounting parts, some were calibrated correctly, some weren't, the factory fix was to trace back to the process line numbers and see which line had the "Characteristic" and which didn't and see where a common denominator was found .... look at what was different on that particular line, and rectify the problem .... no more "Characteristic" models coming off the production line.
If that theory is correct, the only possible solutions is to mask the problem until things loosened up enough to naturally absorb the resonance, or not actually be able to transmit it because the tension between the misaligned parts has eased with wear, a complete new chassis would be required to actually fix the problem, that would involve virtually replacing the unit with the "Characteristic" with a unit constructed after the issues were sorted.
Possibly the suspension mounting retro fit sorted some of the models where that part was welded up out of position, but if it was a motor mounting out of position, or a combination of the two, nothing is going to solve that issue but time for the parts to loosen up ...... or simply biting the bullet and giving the customer a replacement vehicle ....... That would be a factory thing though, not something a state or country distribution mob could do .....
Having worked in various manufacturer's new car workshops, I've witnessed some really strange work-arounds to disguise a fault .... from reaming out the metal centre of a bush to allow a trailing rear wheel on a FWD to find the angle it liked rather than shredding the tyre, to off setting the rear gearbox mount to shift a vibration caused by the two halves of a stretched body model not actually being welded together square

all the way to filling a body cavity with mastic to stop a water leak caused by the two body panels not being spot welded together properly and allowing the seam joint to open up under certain conditions ..... can't say which brand or model ... one of those NDA type things, but back in the '70s they didn't have fancy names for it
T1 Terry