When the shield is on the player's off-hand, and the player blocks an attack from another player, a mob, or a TNT explosion there is no blocking animation. See the comparison between the main hand shield and off hand shield blocking animation.
Steps to Reproduce:
- Spawn a hostile mob
- Equip a shield in your off-hand
- Switch to Survival mode
- Block an attack from the mob
There is no blocking animation.
There should be a blocking animation.