Chickens crazy

Using a dispenser to throw about 450 eggs in a space of 1x1, I obtain several chickens, one over the other, motionless. Simply just grow a chicken to make them mad, start going through the blocks around them. This did not happen before, and it made my farm automatic chicken did not work.

See picture 2 and 3 that the single group of chickens was transformed into four groups, but when they grow to full adult size they can exit the glass. Some updates ago it did not happen.