Same symptoms, same solution here.
On the day of the issue I was running a demanding workload. When the throttle to 400MHz kicked in, I thought it was frozen outright.
After applying the paste, it’s sitting at about 85ºC at the same demanding workload. Not sure what the temps were that made it kick in in the first place…
Anyone know if it’s possible to see the throttle in BIOS? The throttle persisted through multiple reboots.