Subtransactions allocated to nonexistent main transactions

What causes this issue?

Checks for <DS:DE.HVORG_KK>main transactions</> that are not maintained
in Customizing even though there are
<DS:DE.TVORG_KK>sub-transactions</> allocated to them.
When you maintain sub-transactions, the system ensures that only main
transactions that have been maintained can be entered. If these main
transactions are subsequently deleted without deleting the related
sub-transactions, an inconsistency results.

How to fix this error?

If the system finds an inconsistency, you have the following options:
Complete the missing main transactions.
Delete the sub-transactions that refer to main transactions that no
longer exist.

Error message extract from SAP system. Copyright SAP SE.