Entities sometimes do not render behind the wither armor effect of the Wither

The bug

Since the Wither's "armor effect" is translucent, entities behind it will sometimes disappear (does not render).

How to reproduce

1. Run the following command:

    /summon wither ~ ~ ~ {NoAI:1b,Health:150.0f} 

2. Spawn a mob behind the wither
3. Observe
   → The mob disappears behind the wither's armor effect.