This is expected behavior. When you fire an Event (using a Fire Event Activity in an Automation or defining a schedule for the Event), a 'High Water Mark' is added to last record in the Data Extension. So, the next time the Event is fired, only new records that have been added to the Data Extension will enter the Event. Refer to this help document (specifically the 'Contacts fell below the High Water Mark' section) for further information.
However, this might be OK for your intended use. When you fire an Event, the Contacts in your Event Source Data Extension will be evaluated by the Event and providing they meet the Contact Filter Criteria (defined in your Event), then they will enter the Event.
I'm assuming that you published the new Interaction after firing the Event, in which case the High Water Mark was set on the Data Extension and the Contacts will not enter it. However, if both Interactions were published, then the Contact would enter both Interactions when the event is fired.
However, if you want all Contacts to be re-evaluated each time the Event is fired, then you will need to create a Query Activity (and include it in an Automation) to target the Event Source Data Extension and overwrite the existing records, which essentially resets the Water Mark.
Regarding the 'view event results' behavior, I'm also seeing this in the current release. You're correct in that it should indicate the percentage of rejected Contacts (that did not meet the entry criteria) and the percentage of Contacts that would have been accepted into the Interaction, but it appears that this not working at the moment.
The answer is: there's nothing wrong with the steps I wrote. Marketing Cloud was just not working properly for an entire day of work. I logged in the next day after the answer/comments from @vikal, and started testing again, and it's now working.
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If I remember correctly it's based off of Contact ID but if your contact's email address changes they should still be prevented from entering as long as their Contact ID remains the same.