I can change a customer number on a receipt in one org but not another

EBS 12.1.3

Receivables. Receipt entry

Form ARXRWMAI

Form Version 12.0.15.12010000.37

Query back a receipt in ledger A / Org 1 and click Apply. I can see the invoices the receipt is applied to and can untick a line and create a new line for ANY customer number - not just the one the receipt was created for initially.

If I do the same thing in ledger B / Org 2 then I can only see the customer number that the receipt was entered for initially. I feel the latter is more correct but users have been using the former to make receipt adjustments and have asked why its not possible in ledger B.