ISO code & belongs to another dimension

What causes this issue?

The ISO code for units "&V1&" is already in use in dimension "&V2&".

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?

Use the ISO codes for units of measure only for units of the
appropriate dimension. If necessary, change the units of measure for
dimension "&V2&".

Error message extract from SAP system. Copyright SAP SE.