To reproduce:

1. Put the command:

   execute as @a[x_rotation=-90..-85,nbt={Inventory:[{id:"minecraft:elytra"}]}] at @s run tp @s ~ ~ ~ ~ -85

   in a repeating command block.

2. Look directly up while flying with elytra. It takes some fiddling and a few tries to get this right. You may have to use firework rockets.
   -> See that the arms and legs of your skin are gone.

Notes:

• Your legs reappear whenever you are swimming.
• If you take damage when you are without your legs or arms, they reappear, but will not play any animations.
• If you die, the issue is fixed.