Subtransactions &1 and &2 should have different debit/credit indicators

What causes this issue?

Subtransactions &V1& and &V2& of main transaction &V3& should have
different debit/credit indicators.

System Response

You tried to maintain an aggregated subtransaction as a reversal or
write-off transaction with the same debit/credit indicator as the
original aggregated subtransaction. This is not allowed.

How to fix this error?

Choose an aggregated subtransaction as a reversal or write-off
transaction with a different debit/credit indicator from the original
aggregated subtransaction.

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

Error message extract from SAP system. Copyright SAP SE.