Good to hear the 420D behaves ok when ground is involved.
SDG said he tested it too and found no reference such behaviour. In another post somewhere. So at least we have a trusted public figure saying the same thing

Too bad the issues I highlighted were not public before I purchased mine - or at least I didn't find anything online when I looked. A T3A without the voltage leak and grounding issue would be a nice one.
I said this as a comment on your video also. I would do exactly what you had done if it were my profession. I'm a hobbyist, if I can't solder this weekend or whatever

But if it is my job, I wouldn't have risked it and bought a JBC station.
I honestly think you made the right call.
Even with me or SDG or "..." saying, well I think T420D is ok.
There isn't years of testing, it has been like, what? two weeks.
That is still a huge risk for you to take.
Do you think there is a way to develop a similar station with an SMPS supply without those issues? Just curious.
I've avoided commenting on this because I think I have some ideas to get past it.
But I wanted to test it on the T3A.
My hesitation is that Aixun actually do make really decent designs, they aren't stupid.
So there must be a reason they are using these hacks to get around this, even in the T320.
Instead of say two isolated windings on the SMPS not referenced to each other or isolated DC->DC converter (for logic control or thermocouple ADC). Leading me to think I'm overlooking something obvious.