I've implemented recurrence in my scheduler, much the same as the tutorial (TutorialDayPilotRecurrence) found on this site. The only difference is I'm using MVC, but both implementations suffer the same issue.
The problem occurs when I edit a single occurrence of a recurrent event and adjust the Start value to anything BEFORE the master's Start time. This causes the exception to disappear from the scheduler, even though the exception is properly added to the database.
The converse is not true. I can adjust the exception's End time to any value before or after the master's End time. Even stranger, I'm able to adjust a recurrence exception's Start time to a value before the master's start time using the Resize event without issue. The values entered in my database are identical, regardless of whether I used the Edit page or Resize feature, but using the Edit page removes the exception from view.
This can be reproduced in your Recurrence Tutorial example with the following steps:
1. Create a Weekly recurrent event to repeat indefinitely.
2. Click on one of the expanded events to bring up the Edit form.
3. Choose 'This occurrence only'
4. Set the start time to anything before the master's start time and Save.
5. Watch this exception disappear.
6. Check the database and verify the exception was properly added.
7. Adjust another expanded event by Resizing the Start time and it should work fine.
This seems to be an issue with Weekly recurrence, because it works fine with daily. Any help would be appreciated as I have no hair left to pull out.