You cannot change item &1; item is already assigned (see long text &2)

What causes this issue?

Assignment exist for the item in ARUN_BDBS. Customization for
Unassigning Rule for Goods Issue or Goods receipt is maintained as
Error.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Change the customization from Error to Warning for the fields
requested for change.
Go to SPRO->Cross application components->Advanced available to
Promise-> Supply assignment->Cross Applications->Goods issue handling
(For issue message raised with Goods issue)
Go to SPRO->Cross application components->Advanced available to
Promise-> Supply assignment->Cross Applications->Goods receipt handling
(For issue message raised with Goods Receipt)

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.