The resource pack attached offers a complete fix for this issue. Mojang have my full permission to (and are encouraged to) replace the affected vanilla model files with the contents of the resource pack.

Download resource pack:

• 1.17.1: consistent-coral-fans-1.17.1-v1.0.zip

The bug

The coral fan block models, which are functionally template models due to only containing the block shape and being referenced by other models to apply textures, are not prefixed with "template_". This is unlike a multitude of other template models which the game uses, which are in fact prefixed with "template_".

How to reproduce

This is as easy as just navigating to the assets/minecraft/models/block directory and checking the file names.

1. Open the game jar file using one's preferred method
2. Check the model file of a block that uses a coral fan model, such as horn_coral_wall_fan.json
   1. Note that it references block/coral_wall_fan.json, and also note that it isn't prefixed with template_
3. Check the model of a block such as a wall torch, anvil, chorus flower, ...
   1. Note that the model it references is prefixed with template_ due to the referenced model in question being a template model

Expected and actual results

The table below summarizes the expected file names for the models in question.

How to fix

Fixing this is as simple as renaming coral_fan.json and coral_wall_fan to template_coral_fan.json and template_coral_wall_fan.json, and then repointing all model files that reference it to the new names. 20 different model files currently point to these, for the 5 coral variants, floor and wall differences, and ddead and alive differences. The resource pack attached to this issue contains fixed versions of all 20 of these models as well as renamed coral fan template models to accompany them, meaning these can be added to minecraft.jar in seconds to fix this issue.

The pack also cleans up formatting for consistency, and comes along with a bonus fix:

• MC-203036 - The planes are now mirrored on the rear faces, specifically in a way that avoids undesirable mirror symmetry (rotational symmetry does result, however this is also present in vanilla anyway)