Phrases could not be combined (dangerous goods master)

What causes this issue?

You have tried to combine phrases that exist in the dangerous goods
master. However, the corresponding data record or data records in the
dangerous goods master are currently being edited.

System Response

The phrases are not combined.

How to fix this error?

Ensure that the data records are no longer locked by another user.
Restart phrase combination.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.