'Twitchy' probably isn't the best way to word it, but it is the shortest. So, when picking up an axolotl in a bucket, if you're looking at a block (and would be close enough to interact with it), the axolotl will almost immediately get placed back down. If you're quick enough, that won't happen, but holding the button to interact a tiny bit too long will cause that issue.
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Auldrick
migrated
After experimenting, I don't find any difference between axolotls and fish as far as what happens when you try to pick one up in a bucket, so I'm closing this as a Duplicate of MCPE-44320.