Cylinder head sleeve nut

Why this screw deserre regularly after 200 kilometers?
Several friends have the same problem!
4 years ago, by coming back from the rally to inter Norton in Germany I lost that of the left, without perceiving me, and the cylinder head gasket clicked has this place.

Number 18

https://andover-norton.co.uk/en/shop-drawing/123/engine-cylinder-cylinder-head

Those head studs are always pulling out. Here's the timesert solution. See the triangular reduced shank studs at the end of the video. You should also use Belleville spring washers.

I go, in a 1st time use Belleville spring washers .

Thanks jseng1 for your answer