Error in buffer: incorrect mode '&' in interface table

What causes this issue?

An error occurred when saving data. The input-output-table uses the
incorrect mode &V1&.

System Response

The system is in an inconsistent state.

How to fix this error?

Exit the current transaction (if possible) and write down which steps
led to the error. Notify your system administrator.

Error message extract from SAP system. Copyright SAP SE.