Visual bug when blocking with shield and shield takes damage

I had realized that, in my survival world, when I was fighting skeletons, my shield would show as not blocking even though it was. Later I went into a superflat test world to confirm or deny my understanding.

I found this:

The shield, if it takes durability damage, will look as if its not blocking.

When this happens, it still blocks any damage it would've blocked. (Thus why I see it as a visual bug)

Feel free to ask further questions! You may find more info in the video attached!