Yep slim rubber O ring which should stop the chatter between the metal faces, if you carefully pull and rotate the arm against the spring tension (as if you were adjusting the arm position) you will see the gap open to slide the O ring into, you could experiment with a rubber band or some PTFE tape
The idea is that the space taken by the O ring will add additional tension to the spring
That’s a great tip and one I will try tomorrow. Strangely enough, I have an O ring kit which I had to dig out to repair my lawn mower yesterday. I will raid the box for a suitable o ring to try this fix and report back.
