A Uproc has its Functional Period modified, ie from daily to monthly.
The corresponding Task based on this Uproc does not adjust automatically the processing date to reflect the new Functional Period.
This is expected behavior
The First Task launch after the modification will keep its processing date , this is normal, as it had been previously created by the Calculator.
The Functional Period modification will be taken into account on the next launch of the Task.
If you want the calculator to take it into account right away you need to Disable / Enable the task.