Summary:

Sometimes when you want to pick up an axolotl or fish in a bucket, you will pick them up in a bucket, but they will automatically be released. This happens sometimes and just in the water space, but most often when the mob is near the block.

Steps to reproduce:

1. Place the fish / axolotl in the water one block high.
2. Try to pick it up with a bucket.
3. If climbed into the bucket, repeat again.

Observed results:

Sometimes (almost always) the mob will automatically be released from the bucket.

Expected results:

The mob will not automatically release from the bucket.

Video:

Minecraft 2021-03-31 22-20-38.mp4