Forge version:
Twilight Forest version: (this is the build number)
Link to crash log: (please use a paste site such as gist, do not attach the .txt or paste the log inline)

Steps to reproduce:

1. find a naga boss

What I expected to happen: to see the whole naga boss

What happened instead: you can only see its head

are you using optifine?

yes, Is that the issue?

indeed. Optifine ruins some things in the mod. We cant fix these issues sadly. For the full experience I would recommend removing it.

good to know.

Oh, it so sad .(( I will try another optifine version, maybe it will help.

And another question, Naga breaking blocks of labirint and surroundings , its normal?

Yes

It will be fixed in future? Or it impossible?

We can't fix it, it's an optifine issue.