Editing a task which already has a reminder, duplicates the reminder.
If I add a reminder to a task (as pictured):
Then add a second reminder, leave the task and reopen the task - you can see that the first reminder is duplicated:
This also happens when a reminder is set, then something else that is not a reminder is changed. For example if changing the due date, the reminder dates are duplicated. (Need to leave the task, then re-open the task to see this happen).