Magma Cube's layers UV mapping overlaps

Segments 1, 2, 5, 6, 7, and 8 of a magma cube overlap with each other, causing problems when modifying the texture in a resource pack.

Steps to Reproduce:

1. Download and apply the provided resource pack:
   MagmaCubeOverlap.zip
2. Summon/spawn a magma cube
3. Wait for it to jump, and spread out its model
4. (optional) freeze the game

   /tick freeze
   

Observed Behavior:

The top and bottom faces of the previously listed model segments will be textured incorrectly, including the front and left sides of the previous segments before it in the texture.

Expected Result:

Each model segment could be modified separately from one another, without any overlap.

Screenshots/Videos:

Notes:

Related to MC-256371 MC-271509

Old Description:

The description has been modified, because the previous one was fairly messy and over descriptive. I have left the old description in a pinned comment here:
https://bugs.mojang.com/browse/MC-225367?focusedId=1337489&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-1337489