Ok, it looks like the event was "Closed" then "Removed" by the leader before the event's date. 
But some other people was not logged when he deleted the event, and they want to broadcast the event. 
As soon as they bcast it, the leader realize he deleted it, and broadcast again the deletion. 
This looks normal to me, except that you are right, it triggers the 'N' new event flash in the minimap. 

I guess I have to find a better way to prevent that from happening