In version 1.10, a feature was introduced allowing you to set the FallFlying NBT tag of mobs to 1, enabling them to use an elytra when equipped. However, when upgrading to the 1.20.5 snapshots from previous versions, the FallFlying NBT tag for mobs is reset to 0. As a result, all mobs previously configured to use the elytra will cease doing so upon upgrading to the latest version.

Steps to reproduce

1. Load up 1.20.4

2. /summon husk ~ ~ ~ {FallFlying:1b,ArmorItems:[{},{},\\{id:"minecraft:elytra",Count:1b},{}]}\{code}
    # Update the world to the latest snapshot version
    # 

   /data get entity @e[type=minecraft:husk,limit=1,sort=nearest] FallFlying{code}

Observation: The tag is now set to 0, despite being previously set to 1. Consequently, they will cease using the elytra.
Expectation: The tag should remain set to 1, ensuring they continue using the elytra.