I think Holmes4 likely nailed this problem! In case it’s not clear, I’ll restate:
RCDs in Europe are the same as GFCIs in the US but with a couple of differences. The major difference is in the trip threshold. RCDs in Europe trip if over 30ma leakage current to ground. GFCIs in the US trip on leakage current over 5ma to ground…
The link that Holmes4 posted indicates Bambu experienced some challenges with the heat bed heating element insulation: at 120V the electrical insulation is sufficient, but at 240V there can be enough leakage between the heating element and the grounded heatbed to approach or possibly exceed the regulatory limit of 30ma.
Bambu derated the heatbed from 110 to 100C on 240V applications as a work-around. At lower temperatures, the problem is less likely to exhibit.
My best guess is the heatbed heating element on your printer is beyond spec. It has too much leakage and that is causing the problem. I suggest contacting Bambu support and seeing how they want to proceed.
There is little sense in using a watt meter to measure printer power draw. If the printer was drawing in excess of breaker capacity (63A), you would definitely know it from the smoke, loud pops and bright flashes. This would not be anything subtle 
If you have a DVM or milliamp meter, you could measure current flowing on the ground between the printer and the outlet. If you do that, you will probably see current on the ground start at zero when the heatbed is ambient and then begin to rise as the heatbed gets hot.
If you see that current get to 5ma, that would be a concern and I would personally consider that heatbed defective. If it starts to approach 20-25ma, you have definitely found the problem. You would never actually see it reach 30ma, because that would cause the RCD to trip.