Migration of the customer G/L tables is still running in the client &1

What causes this issue?

You cannot start the migration in the current client because it is
currently running in another client. You can only run the migration in
one client at a time.

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?

Finish or reset the migration in the client listed in the message.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.