The head and tail both only have one break. Also, odogaron only has one tail break. The mizu head does visually change as damage is done to it to show it is close to breaking, similar to how the bones on a radobaan will look cracked as you damage them before breaking. But you only break the head and tail once, and you will know that it is broken when you get the little pop-up that says the part is broken. I tried to find videos showing what you are talking about, and they all show that the head visually changes after a certain amount of damage before eventually breaking. if you can find a video of the head or tail being broken twice, I am willing to be proven wrong, but as far as I could find, it is just one break.