https://www.youtube.com/watch?v=Rn8z_iQDIn0

As you can see in this vod i recorded while playing this axolotl spawn into this pond of water, but  randomly while i follow him he seem to dissapear, just to reapper later.

The first time it happen it disappear while walking inside 2 blocks of dirt. I wasn't recording back then, but as soon as i saw it i had to record this strange phenomenon. 

This world was created on snapshot 21w17a, but it could be possible it's present since axolotl release.

I'm no programmer, so i can't be sure, but is it possible the animal clipped into blocks? Are the collisions funky?