I had updated to ETF version 5.0, when this happened, i downgraded to 4.6.1 and it worked flawlessly

Emissives on Player entity become non-emissive when player blinking frames play
after reload of client, resource packs fail to load

Emissive textures broken
Playing multiplayer, updating mods to latest versions
Screenshots

• Minecraft version: 1.20.1
• ModLoader: quilt 0.22.0
• ETF Version 5.0
• Does the issue persist with only ETF installed? || Have not tried, and I don't want to. If other people have this issue, i may provide a mod list to look for mods in common
• Have you checked the FAQ in the Readme, or Discord, to see if it is a known issue? I will after this is submitted

I have this issue too. I haven't really tested it, but I do use 3d Skin layers if that's the issue.

I did a bit more looking into it, and it seems to be caused by Iris and somewhat ImmedietlyFast.

When I first removed Iris, the emissive pixels were transparent other than when blinking. I got rid of FA and it worked great. When I added Iris back, the horns blinked again.

IF & Iris: Eyes and horns glow and blink. Transparent in the inventory menu.
Just IF: Eyes and horns are transparent but still blink. Transparent in the inventory menu.
Just Iris: Eyes and horns glow and blink. Not transparent in the inventory menu.
Neither: Eyes glow and blink, horns glow without blinking. Not transparent in the inventory menu. Working as intended.

Literally everything here has been fixed by updating my mod versions. I am horribly embarrassed and would very much like to delete everything I said, but I think this could be valuable for the next me that rolls around. Update your mods ya'll

can i get the affected skin