I am having a similar problem, I is not just with arrows, I believe it might have a part to do with the way it receives 'redstone' signals, because like with the arrows my 'auto-armor-equiping-machine-thingy' will fire once out of the two bottom dispensers, but upon second attempt, they do not shoot. I have made it several different ways. It's as if the dispenser temporarily holds a 'redstone' signal. Hope this is helpful, and I hope it can be fixed...
Nick Sorah
I am having a similar problem, I is not just with arrows, I believe it might have a part to do with the way it receives 'redstone' signals, because like with the arrows my 'auto-armor-equiping-machine-thingy' will fire once out of the two bottom dispensers, but upon second attempt, they do not shoot. I have made it several different ways. It's as if the dispenser temporarily holds a 'redstone' signal. Hope this is helpful, and I hope it can be fixed...