Valve Set screws, type 1 engines M8x1
This parts must be replaced more frequently. through which the screw has a radius, he gets a flat spot.
When you go adjust the valves with a screw with a flat spot, turn the screw and the play is gone. But because you sit on the tip of the flat wear spot the screw wear even faster.
And is your valve lash again too big, and rattles your engine.