Conversion of unit of measure & to & for mat. & & not possible

What causes this issue?

It was not possible to convert various units of measure in the period
records into the current unit of measure for the material.

How to fix this error?

Check the entries in table T006 and the alternative unit of measure in
the material master record. If this does not help, inform your systems
administrator.

Error message extract from SAP system. Copyright SAP SE.