No detailed lock could be set for characteristic '&1'

What causes this issue?

To set the lock for data selection, you can only use characteristics
with unique attributes for the selection. At least one of the
characteristics in your selection does not have unique attributes, and
can therefore not be used for the lock. For this reason, it is possible
that more data will be locked than the data you want to process.

System Response

As long as this lock exists, no other user can change this data.

How to fix this error?

In your selection, include as many characteristics with unique
attributes as possible. If you are not planning on changing the data,
then you should switch to display mode. No locks are set in display
mode.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.