When attempting to "Undo last schedule" for a scheduled program, the below error message occurs:
"The event could not be deleted: Tickets to the event have been sold."
This occurs although no program events have been sold or placed in a user's drawer. For example, you go to Tickets > Program search and select a program. You then click "Undo last schedule" and the error appears.
If you are still experiencing this issue, Chat with Support and reference this article.