I tested to see why this happened and saw it was because the mod Essential (Fabric).
There probably wont be a fix to this issue, but if there was a option in the in the config file to "Disable All Hats" in firstperson, it would be a nice fix for Essential and other mods that mess with the playermodel. If that's possible to implement.

Here's an example:

I'm having this too, and it's very irritating! I have the antlers on my skin, and they're covering up the screen a lot.



And the Essential cap is one of the worst, as you've seen in the pictures

This needs to be fixed from Essentials side. They render the hats incorrectly.

Could it be possible to shift the hat part of the playermodel behind the camera in first person? If it's behind the player they cant be seen at all even if a mod renders hats incorrectly; Or make hats so small that they can't be seen at all?

Maybe it could solve cases like this if mods dont work as intended with this mod, Even as a band-aid fix.

Could it be possible to shift the hat part of the playermodel behind the camera in first person?

And that's exactly how all helmets/blocks on head/mod cosmetics usually get hidden(for vanilla stuff I just skip the rendering). But essential clearly doesn't use the vanilla render logic, so it doesn't work. This is not a bug of this mod, this is an Essential bug.

Please report this issue to them, so they can look into it. I can't fix this for their closed-source system.

Tested with the Essential cap, can not reproduce anymore on 2.2.3.