MS1Corp
Yes, because you are doing a full edit and not an inline edit. Inline edits allow you to update just the singular field by clicking on it in the header. Unfortunately the issue summary is the only field we don’t have inline edit for so you have to do full edit like you are doing. With full edits every field is technically being updated at once; only the values that change actually get updated. However things like date fields get recalculated especially the due date field. So, yes, a due date is already set however the date is in the past which is not allowed when setting the value - which you are technically doing when doing a full edit.
That is an over explanation however I hope it helps you understand how it works.
Cheers.
