What happened?

I apologize in advance for mistakes, my English is very poor.
My problem is that when I use a build of more than 50 mods, the animation problem starts while sitting on a horse.
If I add 49/50 mods to the assembly, everything is fine, if at least 1 more mod. then the problem starts
The animation itself then looks like I'm sitting in a boat (no body curves, but just a sitting animation)
no matter what mods I exclude, more than 50 mods fail

What should happen?

Help me🥺

Mods

1.16.5
using farming based survival build

SWEM Version

Swem-1.16.5-0.5.3.0

Singleplayer or Multiplayer

• Singleplayer
• Multiplayer
• Other (Please add a comment to the issue where this is happening)

OS

Windows

Relevant log output

No response

Does removing any other mod than toolbelt still produce the same error?
So what if you removed vehicle-mod, does it still look like the boat animation?