Custom models become invisible when seen through any shader

As you can see in the attached videos, models on armor stands become invisible after going through the custom or default shader.

How to reproduce:
Summon any entity and give it an invisibility effect, then while in spectator mode look at the model through that entity.

/summon minecraft:zombie ~ ~ ~ {NoAI:1,Silent:1}
/effect give @e[type=minecraft:zombie] minecraft:invisibility 1000000 0 true