Bugs of the scheduling function

Here is a demonstration. When I set a schedule, the function works fine.
Screenshot 1

When I switch to a later time, the function works fine too.
Screenshot 2

But when I switch to an earlier time, it becomes:
Screenshot 3
The original line does not change. Instead, there is a new line appearing in a different block.

If I delete the wrong line and then switch to an earlier date, the same thing happens
Screenshot 4 .