Judging from the phenomenon, it is a heat dissipation problem.
It is 50 degrees when not plugged in. What is the temperature after plugging in? I told you how fast this crazy rotation can go. Take a picture of Master Lu and see. First, look at the temperature, and secondly, look at the rotation speed.
If you really think it is not a heat dissipation problem, you can remove the SSD, replace the mechanical hard drive in its original position, and see if the fan spins wildly.