I am pretty sure this started when the last version 1.12.1-5.3.12 was released. I am not 100% certain it is this mod, but thus far it is my best guess based on my experimentation. When you go through a portal and then return, all the animals are invisible. I can hear them, but not see them.

I am using the Fantasy Evolved II pack: https://minecraft.curseforge.com/projects/fantasy-evolved-ii

Here is video: https://youtu.be/6hcu7kUqpFs

NetherPortalFix only affects vanilla's nether portals, not portals from other mods, so this is more likely to be an issue in the Hunting Dimension mod itself.