Arm animation is not executed in certains circumstances. Which are:
Dyeing a sheep, or wolf/cat collar
Shearing a sheep or mooshroom (not fixed, see MC-160896)
Dropping an item (not fixed when dropping from GUI, see MC-160897)
Emptying a water/lava/fish bucket.
Filling a bucket.
Placing a boat.
Throwing an ender pearl, snowball, or potion.
Throwing an eye of ender.
Feeding an animal. (not fixed, see MC-160895)
Making tamed animals sit/stand (not fixed, see MC-160981)
Activating redstone ore (not fixed, see MC-161151)
Crossed circumstances have been crossed out, those who are not are still not present in the game.
Related issues
relates to
Comments

@unknown, that's MC-123352.

There is still residue of this bug in 19w37a.

Confirmed in 19w37a

I'll test it and make corresponding reports for the remaining bugs.

I updated the report with remaining issues.


I think it'd be easier to have everything in the same ticket, for the sake of consistency and helping devs
I decided to leave this ticket closed and keep the newly created tickets by @unknown. Otherwise this ticket might become a mess later if even more circumstances in which this happens are discovered.

Can someone add 19w37a as the fix version? Thanks!
Whoops, removed it by accident. Done.

MC-160981 is another case that could be listed.

MC-161151 is another one
They're linked as related, that should be enough.
The animation is also missing when interacting with a door while crouching.