Surface Pro 7 trackpad freezes

I received a new Surface Pro 7 8GB 128GB on 27/03/20. The trackpad cursor freezes after a very short time of use on mains power. Cursor unfreezes with power cable is removed. My SP7 is fully updated from Windows update and no other software installed.

Going to Microsoft Support and speaking with a chat agent, I completed steps of running diagnostics and resetting the computer. The problem remained just as bad. The agent decided it was a hardware issue and authorised a return. A new SP7 arrived today 31/03/20 and it has exactly the same problem! In fact it is worse, in that the cursor goes into frozen state more quickly after I attach the power cable. Further chat with agents - they are going to send me a new power supply. But I am dubious that will help.

I like the Surface Pro 7, and it works great on battery power, but is frustrating that the trackpad is completely unusable while on mains power. I suspect some manufacturing fault of inadequate shielding of the trackpad from magnetic interference caused by the power supply. But who knows? I have Surface Laptop 2 and have never had any problem with its trackpad while on mains power.

The last Microsoft chat agent told me my case would be escalated to a more advanced technician. I mentioned that there are over 200 people reporting the same problem in https://answers.microsoft.com/. See http://tiny.cc/u5f8lz He said they have nothing about this problem in their database.