I figured out the problem, it was a defective Hyper 212+. I swapped it with the other one I have and now it's loading almost 10C less.
Which gives me now some OCing headroom.
The chip also failed 6 hours in at 1.36v and 3.7GHz, Priming and Linpacking.
At 3.8GHz it's getting about 63.5GFLOPs on linpack.