This is one of the biggest problems with redstone. if you build circuits with pistons and other entities like hoppers and droppers in operation the circuits produce different outcomes which is undesirable. If a circuit does something once it should repeat that function forever consistently.

As an example see attached picture.

I was messing around trying to find an alternate t-flipflop and had this configuration. it's two sticky pistons and a cauldron. The observer is looking down observing the placing and removing of the red block. if you repeatedly break and replace the red block you will see that the cauldron does not swap location consistently. sometimes it does other times it does not.

This lack of predictability in redstone right now is a major problem for the redstoner community.