Latest version of Better MC 1.16.5 is crashing when attempting to render the yak from environmental. Removing the resource pack resolves the issue. Pastebin of the relevant part of the crash here: https://pastebin.com/eMt4ZELb

Thank you for reporting! This has been fixed now and I've uploaded the safe version of the pack to Curseforge.

Surely it wasn't actually crashing, just logging the exception?

I've just checked this and on my singleplayer world the faulty version didn't result in a crash - it just logged the exception like you said.
So I'm unsure if the issue is solely with the resourcepack, but at least it shouldn't occur again.

That's what it's supposed to do, so I hope that's the case lol
Thanks for checking!