Activating elytra whilst walking backwards causes the player to face backwards as shown in the video.

Steps to reproduce:
1. Equip an elytra in survival mode
2. Go into 3rd person mode (front or back)
3. Walk backwards
4. Try activating the elytra by jumping
5. See the player turns to face the direction you were walking in (backwards) then flips to face the correct direction. This flip only happens for a very short amount of time at the beginning of the falling/transfer-into-flying animation