This machine was fine for a long time.
I took it on the road and experienced the problem again.
With a few slaps on a table screen side down I managed to make it
usable.
This problem is very likely a mechanical instability.
Now still my fan comes up pretty high but not to the point of shutdown.
Perhaps the problem is at the inlet ports where the sink contacts the
body of the machine. The spring loaded heat sink looks like a strong
design; probably stronger than what it is mounted to.