Find part on shock absorber.. Polting while driving

Hello forum, I have a question for you !! and I am looking for this part at the shock absorber. I marked red at the picture. Is the plate on which the counter nut is screwed up. I already looked at Ebay but did not find. Because have the problem that when I hit the steering wheel and drive over cobblestones or deeper potholes, always have a poltern. Had the car recently on stage. When I touch on the wheel top and bottom and the wheel to me and direction S The game is above. I’ve already changed the cathedral camp on suspicion. Now it doesn’t pollen as much as before, but it’s still there. Poltern comes from VR. Fall and track I have set. Game is still there. Spring is fine. Shock absorber looks good as far as possible (no oil exit). Cross handlebar jack is cut off soon, on both sides with support joints. But before that, I want to know why the Vilt. but shock absorber defective ?? Presumably but somehow this funny plate is at the top of the cathedral. Do you have another good tip. Be happy about every answer. Thanks already in advance.