It seems that somewhere between 0.2.24 and 0.2.28 the data models for the ender dragon and wither have been corrupted. Not sure if these were intentionally removed as i didn't see mention of it in the patch notes, so just in case its a bug I'm raising the issue.

creating a new world seems to also have the same issue, so it doesn't seem to be related to updating

Can confirm, already made dragon and wither models are now broken

There are a few more than just the two you reported. I had 7 broken data models in my storage system. Not sure which ones exactly they all are, but I suspect its related to the recent changes.

Yeah it seems quite a few of the models are now missing from JEI as well as corrupted in game.

Happened for me too, seems to the 7 models defined in /kubejs/data/hostilenetworks/data_models, so ender dragon, evoker, skeleton, warden, wither, wither skeleton and zombie.

Corrected in PR #959 will be in the next pack update

Thanks for the quick fix!

Updated my save using the changes made in the PR and all the models returned to normal :)

Running
/hostilenetworks datafix_all
and replacing the files with the newly generated files also fixes the issue if you don't want to update to the pr.