Precision 7710 - CPU i7 -6920HQ overheats constantly

Dear Community,

the CPU i7 -6920HQ of my Precision 7710 overheats constantly. This has been the case since a few updates (Unfortunately, I don't know since which one). I have read that it could be due to a faulty thermal management. The temperature sometimes jumps back and forth between 45°C (113°F) and 91°C (196°F) every second, which actually makes no sense, at least to me. During graphics-intensive applications and rendering, the performance sometimes goes completely to its knees, or the computer simply shuts down without a warning message.

I have run many tests and the hardware should be fine. For most graphics-intensive software, such as Adobe Suite or 3D software, the additional internal GPU card, the M5000M, turns on anyway. This has no heat problem and runs fine.

I have now completely disassembled the computer 3 times and also replaced each time everywhere (CPU / GPU(second card)) the thermal paste (with Arctic MX-4). The fans work and the whole ventilation tract is very clean.

All feasible updates (also firmware) I have made.

But the problem remains.

What else could be done?

Of course I thought about replacing the CPU and maybe installing a stronger CPU for socket 1440 FCBGA. But unfortunately I found out that the CPU is soldered to the motherboard on this model.
And unfortunately I don't know anything about soldering. I would not go that far then.

Does anyone have any other ideas?

Thank you very much,

Bernd