Task with date can't be set to "no due date"
If I have a task that has a date assigned to it and I try to set it to "no due date" by erasing it, this will not save and the date returns. So there is no way to wipe out a date as is.
However, I have noticed that if you have a date and you just set the date to "Today" or another like that, then you can erase it to have no due date and it saves. So it is only an error with calendar dates.
thank you for your report, I have forwarded it to the developers.