I figured out what why it wasn’t working. One of the tasks runs from 7:30PM to 10:00PM. The other task runs from 8:00PM to 1:00 AM the next morning. But when you put in the 2nd task in the form that way, it must think that 1:00 AM is the same day and is before 8:00PM, therefore not a valid time period. Changing the end of the 2nd event to 11:55PM fixed the problem.
However, in real life the event ends at 1:00 AM the next day. Might there be a way to modify the task form so that you can have a task that starts on one day and ends the next day? I am using the multi-day event type.