My guess is it's the Battle for Naboo tag that's messing things up. The event Jar Jar does indeed have the Gungan tag, but he's missing the Battle for Naboo tag, which all the others have. And since the map we're fighting in during the event is Naboo, my guess is there's some kind of mapping going on there, causing Jar Jar to lose the necessary synergy.
Edit: This tag is also the one thing that's changed since the last event, adding to the likelyhood (in my mind) that this is what's causing this event to be different from the previous.