No changes saved - line item & was cleared in the meantime

What causes this issue?

While you were entering changes, the above-mentioned line item was
cleared by another user. As a result, it is no longer guaranteed that
all changes are still allowed.

System Response

The changes are not carried out.

How to fix this error?

If your changes have become unnecessary through the clearing, no
special action is necessary. Otherwise, you can call up the document
again for further changes. Then, only the fields for which a change is
still allowed are ready for input if the corresponding line item has
been cleared.

Error message extract from SAP system. Copyright SAP SE.