Internal unit of measure & cannot be converted

What causes this issue?

The internal unit of measure &V1& in the master record could not be
converted to a external unit of measure in your logon language.

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?

Ensure that all internal units of measure in table T006 are translated
into external units of measure in your logon language.

Error message extract from SAP system. Copyright SAP SE.