Describe the bug
Recently i made 3D modeled chests for my texture pack, which includes a 3D ender chest with a slightly translucent ender-portal texture on the inside.

Today i updated the game to 1.21.1 and all my mods with it. The translucent texture is completely invisible:

List and link to broken resourcepacks
https://modrinth.com/resourcepack/nautilus3d

Expected behavior
When i made this a few days ago i was still on minecraft 1.21 with EMF 2.1.3 and ETF 6.1.3
Looked like this ingame, at the time: (screenshot from a few days ago)

Looks like this in Blockbench:

(please complete the following information):

• Minecraft 1.21.1]

Installed mods:

This is what i get in the log when starting the game:

Please tell me if you need more info.

Update: I got it working because i had to redo the entire model and noticed that the texture was placed on the underside of the element. Although translucent textures are still not working i think?

Blockbench shows the texture is slightly translucent, but ingame it renders as solid. Did i misconfigure something?