Invisible decal trims

[ActuallyBlue]

What happened?

With decal textures enabled via a datapack, if you put a trimmed chestplate and leggings together, the trim on the leggings will disappear.

Screenshots

No response

Log output

No response

Minecraft Version

1.21.4

Iris Version

1.8.5

Operating System

Windows 10

What is your GPU?

AMD

Additional context

In some rare cases, some combinations can affect multiple other parts, and some view angles are able to make them reappear, but it seems too complicated to find consistency in due to it all seemingly relying on very specific scenarios.

Issue starts occuring from MC-1.20.4, only tested with the latest Iris versions
Multiple people I know have this issue.

[Swedz]

I haven't been able to reproduce this with vanilla armor and trims, however I can confirm this does happen with my nano armor set in Extended Industrialization - but only when the armor is rendered in world. When the armor model is rendered in the inventory in the smithing table or player inventory when worn, it's working as intended. Here is how I render trims on my armor set, it seems to be done exactly the same as vanilla armor models, so I'm not sure why it would be a problem with Iris.

Tracking this issue on my repo at Swedz/Extended-Industrialization#140