I'm playing in a singleplayer world. I named tagged my axolotls and put them in a 2 block deep pond. No leads. I went to work on my mineshaft not far away and when I came back only 2 out of 5 axolotls were left. Not all of them disappear but some did. I'm so sad because I saved them from the caves and now they're gone. Some say they even put them on leads and they still disappear. I heard this issue has been fixed but from what I see it hasn't been fixed! Though I am playing on optifine 1.17.1. That may be the problem.