Chicken's wings detach when flapping

A chicken's wings detach from its body when flapping (as in there is a gap between the body and the closest part of the wing to the body. See the screenshot for what I mean.

Steps to Reproduce:

Summon a chicken in the air by using the following command:
/summon minecraft:chicken ~ ~20 ~
→ Notice how the chicken's wings detaches from its body, as it falls down to the ground.