The total cannot be locked (see long text)

What causes this issue?

You want to lock the total of the period screen. This is not possible
in this case, as this value contributes to a locked total or subtotal
on the overview screen and it is not possible to lock another summand
on this screen. A change to the total of the period screen (= summand
on the overview screen) cannot be redistributed to the overview screen.

System Response

You can only lock this total if you remove the lock on the subtotal on
the overview screen or alternatively if you remove the lock on another
summand of the subtotal.

How to fix this error?

Note that totals on the period screen are also summands of subtotals or
totals on the overview screen. If a subtotal or total on the overview
screen is locked, changes to a total on the period screen have to be
transferred to the other summands on the overview screen in order for
the total on the overview screen to remain constant. It is therefore
only possible to lock a total on the period screen if the total or
subtotal on the overview screen is not locked or if there are at least
two other unlocked summands on the overview screen.

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.