I don’t think Ive ever noticed this plastic wearing ring , I’ll have to have a look on monday.
This forward and rearward slop(i call it trailer slapping) you are talking off could this be a cause of the plastic wearing ring? As Ive encountered this movement but i thought as long as the jaws are shut - the trailer is going no-where.
I get under the trailer with a torch and check the jaws, i never used to do this but a agency fella told me a horror story so i check the jaws all the time now. It really should be a compulsory check but most folk don’t do it, well the ones i see anyway.