That seems like a very sound theory for them to test. I know they are working on the issue, so they "may have" figured out the root cause by now, or they may not. I am tagging @CobaltDragon and @Sarumonin in this thread for you. Either CobaltDragon may see it, or Sarumonin may pass your theory on to him for testing, if they haven't already confirmed or ruled out the possibility that part of the programming is allowing the additional entry, but then another part of the programming is booting them back out for too many entries.

As an FYI to all :
I had to scrap the extra Dungeon Entry Event, it will now be a Triple Vanguard ( items, gold, and Rep credit) Event for the same duration.