Cam bolts stripping.
In the past I have had problems with the Allen part of the cam bolts rounding off.
So when I remove the bolts I make sure that my Allen tools are high quality with no ware.
But that didn't help me this time.
This is the second time that I have checked the valve clearance on my SE. This time I wanted to record the shim sizes so I could plan ahead for when I might have to change a shim.
I was using a brand new Allen tool. I held the ratchet head in place. But the Allen head stripped out anyway. The bolt didn't move from its factory setting.
So now I have a few months to figure out how to remove the bolt.
It really seems that the 950 cam bolts are unacceptably soft.