I've got a feeder inside a medium on top of the inner cover. It's been fine for the last couple weeks, but this evening when I filled it, I set off a robbing frenzy. I couldn't tell where the bees were coming from. To be honest, it appeared as if they were coming up from the landing board straight up to the top entrance. Can a hive 'rob' itself in this manner? Could it get so worked up that it would appear like robbing? It's entirely possible they were coming from one of the other 4 hives, but everyone else looked pretty calm and tucked in for the evening.
Anyway, I closed off the top entrance and reduced the lower and the frenzy subsided.