After the release of Minecraft 1.21, custom moss carpet models are broken and have rendering inconsistencies.
Normal Moss Carpet: Culling works, but transparency is broken.
Pale Moss Carpet: Transparency works, but culling is broken.
This conflict makes it impossible for models that rely on both features to render correctly on either block.
Please verify that the resource pack in question fully supports pack version 63 or greater, and if it does upload it here. This report will be automatically reopened when you reply.