Game Version

fabric loader 0.15.3 (1.20.4)

List all installed mods

List of all loaded packs

Nautilus3D V1.9.1 , Default resource pack.

Describe your issue

When breaking a nether portal, for a slight moment you can see the vanilla textures appearing.

Hey, thanks for reporting.
Not sure why it doesn't show the ctm-textures in the split-second when breaking the portal, but i added the center-ctm-texture as the default nether_portal.png. This way it is a lot less visible.
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