Logs: {Link(s) to GitHub Gist, Pastebin, etc with full latest.log and/or crash report}

Steps to Reproduce:

1. Do this
2. Then do that
3. ...

Description of issue:

Well I've been trying to fix the issue by installing optifine, and even going all the way and trying to find out how to resize the beast. No progress. I'll just close this now since I think this is very much likely unresolvable. Thank you.

Well no it's still an issue. What it is is game lag from the path finding from BFL's. Optifine won't solve much. Keeping it until I can solve it.

I had this issue with my tamed ones when I placed them on a Home position on the bottom of a body of water, since the home position has to be on a block.

They like to jump out of the water but the home position kept yanking/teleporting them back and after several minutes of this they would get jittery and stuck.

I fixed this by placing a solid block a few blocks below water level and setting their home position to that. They are now able to leap and swim around just fine, as well as settle on the bottom of the pool. Have not had an issue of jitters in two days. I can make a video and upload if it will help?

I figured I'd leave some info because it seems I'm experiencing this issue as well. I'm playing on 1.16.4.

Mod Version: 1.16.3-1.2.10
Forge Version: 1.16.4-35.1.36

When playing in single player, both Alpines and Royal Reds cause immense lag. Just these 2 dragons cause this. However, on a multiplayer server this problem doesn't exist at all. Just seems to happen on a single player world. Not sure if this info will help, but here u go.

Experience stack overflow on server by leviathan path finding.
I have a report of it if you want it.

( Is there a way to not let some of the dragons spawn or less?
Really wish there was a config file but that might be another matter. )
crash-2021-01-24_18.47.28-server.txt

There probably needs to be some threshold where an aggroed leviathan that can't reasonably path to a player (e.g. player teleported away) just drops aggro instead.

When spawning Royal Reds and giving them targets, I get TPS problems rather quickly once they start flying.

I'm both very glad and worried that this wasn't just on my end. Using the Modpack "Mineshalfs and Monsters" which uses this mod, and upon encountering a Royal Red in the Nether and seeing it chase after another mod and fire its blue flame the TPS makes it impossible to do anything. So much so I had to delete the world since entering the portal or using commands to try and get out of the Nether does not work.

Worth noting that attempting to despawn it by going into peaceful and quitting the game then opening it back up and going into the world doesn't work. The world was in a permanent time freeze.

Just wanted to report I'm having this issue as well. I'm not sure this will add anything but I tested it with no other mods installed on 1.16.5 Forge 36.1.0.

No optifine, nothing. When spawning Royal Reds and giving them targets, I get TPS problems rather quickly once they start flying.

I did notice that adding Performant seemed to have some effect on the behavior, but it's hard to say what exactly is going on. I think Performant will freeze or interrupt entities that are causing severe TPS spikes. With performant running, it seemed like the massive TPS spikes would end with the RR freezing in place in the sky. I'm not sure if this is just the pathfinding AI totally dying or Performant seeing it as a huge problem and stopping it from running.

I doubt this is system specific, but for what it's worth this is on a system running a Ryzen 5 3600, 16GB RAM (currently 8GB allocated to minecraft for testing), and an RTX 3060 Ti.