I'm seeing this issue, or one very similar, in 1.17.1 full release. I've had 4 axolotl's stuck trying to swim through wall blocks for days now (realtime, weeks in minecraft). Every axolotl I put in this pond has the same issue, its just a matter of time.
[media][media]
Also having this issue in 1.14.2, issue occurs when an aquarium in our world is loaded, if the chunks are allowed to unload fish start spawning again.
This issue seems to have come back in the latest version. Currently in a 1.14.2 world, I made an aquarium with ~50 bucketed fish, if anyone keeps the aquarium chunks loaded no squid, dolphins, or any other aquatic mob will spawn in anywhere else.
Can confirm a similar issue, I noticed this happening with all waterlogged fences in a pond I built. Eventually all the axolotls will path find through them and get stuck forever.