Failed conversion attempts: &

What causes this issue?

The number behind the message text indicates how many cluster records
were converted but not exported to the database. The records affected,
information on possible causes, and the necessary activities for error
recovery can be found in the error messages above the current
statistics.

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?

Error message extract from SAP system. Copyright SAP SE.