Please see this recording: https://www.youtube.com/watch?v=CHDUZPQsUAo
As well as the provided screenshots below.

The setting "smooth-animations" in the graphics.yml config file is set to "false" by default. I'm personally not sure what this setting is supposed to do, but I felt it would be best to document it in a bug report since enabling it causes the effects you see in the video where Pixelmon models like the PC, healer, umbrella decorations, and more begin to erratically glitch on screen.

It also appears to have some effects on the models of Pokemon, which I'll provide screenshots of:

https://i.postimg.cc/Jzw9108B/2022-05-26-00-23-34.png
https://i.postimg.cc/g0s5qKZv/2022-05-26-00-18-18.png

In the recording I linked at the top, no other mods were installed but Pixelmon.
In the screenshots I do have other mods installed, but after testing it it still happens without other mods installed anyway.

Of course setting "smooth-animations" back to "false" fixes the issues.

Can confirm - I had no mods and changed only the Graphics config to set "smooth animations" to true, and started getting the same animation errors immediately.

Thank you, will pass on to Internal!