Again, Idk if this bug is a dupe of another bug or not, so just comment if you found it.

The title is kinda confusing. The title means that if you a command block that repeatedly regrow/remove the wool/pumpkin/saddle of the sheep/snow golem/pig/strider then repeatedly apply shears/saddle on the mobs then the mobs will behave weirdly, or more specifically, the mobs will "shake" their head and their body.

STR:
1) Place down an repeating command block, right click on the command block, then type:

execute as @e[type=minecraft:sheep] run data merge entity @s {Sheared:0b}

or

execute as @e[type=minecraft:snow_golem] run data merge entity @s {Pumpkin:1b}

or

execute as @e[type=minecraft:pig] run data merge entity @s {Saddle:0b}

or

execute as @e[type=minecraft:strider] run data merge entity @s {Saddle:0b}

, then set to "Always Active" and then click "Done".
2) Summon a sheep, a snow golem, a pig or a strider.
3) Get yourself a shear or a saddle.
4) Make sure you're on creative mode.
5) Hold down right click or spam right click on the mobs while holding a shear or a saddle.

Observed result: The mobs behave weirdly.
Expected result: The opposite of "Observed result".