Acronis server backup - changing schedule in existing backup plan

Hi all.
I am experimenting with the Acronis server backup software (version
10). I am new to this.
I have made a backup plan with an incremental backup and it seems to
function well.
However the following occurred:
- I recently changed the schedule settings (to have a more convenient
timing) and saved the changes.
- The changes were well entered, however within the backup plan the
"Last start time" and "Last finish time" status both changed to
"Never" after I only changed the schedule of it.
That's worrying, because this suggests that the next time the schedule
triggers an update action it may well make a full update and not an
incremental one, which would make me run short on space.
Does anyone know more about this...?