Relationship structure of & & inconsistent

What causes this issue?

The foreign key relationship between the base tables of a view or a
lock object could not be read.
There is probably an inconsistency because of subsequent foreign key
modifications.

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?

Check whether the foreign keys between the base tables are still
correctly defined.
If this is the case, save the table relationships in the view or lock
definition again and activate the object again.

Error message extract from SAP system. Copyright SAP SE.