Not all of the valuation segments necessary can be locked

What causes this issue?

You have changed LIFO-relevant fields for the current material.
Since the LIFO valuation level in your system is company code level,
all valuation segments of the material belonging to the current company
code must be locked.
However, this is not possible since some of these segments are already
locked by another user.

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?

Cancel your changes and attempt to make them later.

Error message extract from SAP system. Copyright SAP SE.