Data of BAdI &1 is inconsistent

What causes this issue?

The system has checked the data that was processed in Business Add-In
(BAdI) &V1& and has found errors in amounts and/or quantities. Invoice
item &V2& and account assignment &V3& are affected.

System Response

Depending on which BAdI the incorrect data originates from, the system
responds in different ways:
BAdI MRM_PROPOSAL_DETERMINE
If the data is inconsistent, the quantities and amounts of the affected
incorrect invoice item are called and reset to <LB>0</>, and you see a
warning message. You can no longer post the document with the data that
has been set to <LB>0</>.
BAdI MRM_DISTRIBUTION_MAAS
If the data is inconsistent, you see an error message. If you cancel
processing, the system adopts the last valid quantities and amounts.
BAdI MRM_RETENTIONS
If the data is inconsistent, the retention data of the affected
incorrect invoice item is deleted (amount, percentage, and due date),
and you see a warning message. You must enter the retention data
manually.

How to fix this error?

Check your implementation in BAdI &V1&.

Procedure for System Administrators

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.