Table T549s should not be changed after payroll run (payroll area &1)

What causes this issue?

If the multiple employment solution is used it is not allowed to change
the table with the pay dates T549S anymore after the payroll for the
period is already run. Thus make sure that table T549S is changed back
to the initial configuration (which is reflected in the payroll
results).

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.