Shock Absorber knocking noise


I changed out both my rear shock absorbers. 1 was leaking so changed the pair.
Ever since I've noticed knocking clunking sound at back.
The new 1's are pretty much like the stock.
I used the original rubber dampers etc.
I never had issue with original shocks.

Any idea what it could be?

Thinking of replacing the rubber dampers, but having hard time finding some.

Nordschleife NSH225 are the shock absorbers I replaced the originals with.