Comparators don't reliably detect items in dispenser

I'm trying to make a chicken farm which involves eggs being fired from a dispenser. I have the eggs fed into the dispenser (via a hopper) and then a comparator detects that it's got content and fires the dispenser. If there is still content in the dispenser then it fires again and again until it is empty.

However, the dispenser only fires the once: when the circuit is first completed. I can break the circuit and rebuild it and it will fire again but only once. The comparator doesn't appear to be detecting the remaining content. After the first shot it remains unlit. I've included screenshots of the problematic circuit design (which works fine in MCPC 1.8.x).

I managed to create a working version using a different circuit but that has problems in that the dispenser stops firing when there are still ten eggs remaining. Additional eggs will fire but it never drops below ten. The dispenser refuses to fire until there are ten eggs inside. Unlike the other circuit the comparator remains lit. I've included a screenshot of the relevant part.