Reconcile AR Clearing

Please can someone advise how I can reconcile the AR Clearing account. Been using RMA for some time, last year when faulty fabric was returned we started putting it to a DMR. The supplier debit note function isnt being used.
I have checked the posting rules and nothing has been changed.
The WIP report isnt detailed enough to show where the error is accruing.

I am thinking I need help to build a BAQ, to find the issue.