Forge version: 1.12.2-14.23.0.2546
Twilight Forest version: 3.4.239

After leaving and entering the TF dimension (portal was created inside the Naga zone), the Naga was invisible on the client (could not see it's bounding box with F3+B either). A clip of it hissing and breaking blocks can be seen here: streamable.com/4fw5e

I havent seen anyhting like this in 1.16 with the exception of Optifine ruining the multipart rendering (which we cant really fix), so im gonna close this.