I was trying to create a "fire suppression" system using dispensers and a comparator clock, but not all of the dispensers fired. Some fired 3-4 times but still had some splash water bottles in them (from completely full), others were not fired at all, and some had emptied completely. Causing block updates will sometimes cause them to fire, and some fired upon the initial redstone pulse. I know this has been reported before and "resolved" however it is still present for me at least.

Steps to reproduce:
#1: Set up a comparator clock.
#2: Attach to some dispensers.
#3: Fill dispensers.
#4: Activate clock.