Just wanted to put this out there since I was testing each SDK before finding this post. And also try figuring out why this jitter issue is happening in unity and VRChat.

SDK 3.8.0 seems to be the highest update that doesn't have this issue, then from 3.8.1 onward is when it starts to jitter like in the post. (I dont really know unity very well but maybe looking through what changed between 3.8.0 to 3.8.1 would probably solve this issue).

This section is not part of the original post but does also tie to the jitter within VRChat itself:

This VRChat update also seems to have added jitter to avatars (Even on 3.8.0 and below and have not been updated). Although I'm really unable to backup what update was the catalyst for it to start appearing.

But one odd thing I did figure out to eliminate this jitter issue from VRChat was lowering my refresh rate to 60hz (NOT FPS) and that solves the jitter in VRChat but anything higher than 60hz will cause it to jitter.

I found that in unity, the jitter will look bad in play mode but once you've upload that same project in game, the aggressive jitter doesn't really appear but is slightly prevalent in game due to the refresh rate being higher than 60 (Others might need to test this and see if this is also the case for them aswell since I could be wrong).

Also as a side note, the game doesn't really care what your FPS is, at least from my testing. But does care what your hz or refresh rate is.

For people wanting to test this refresh rate for avatars that jitter in game already:

To accuratly test this, you would need to first change your refresh rate then open the game. If you change your refresh rate while in game, the game will still be running the refresh rate you initially opened the game at.

So if you change your refresh rate you would need to close the game, then open the game so it could then run the new refresh rate you set it to.

Just to add to things, this issue is still present in 3.9.0 and 3.9.1-beta.2 of the SDK.

Happens for my avatars as well, jitter depends on scale of colliders/physbones (including the scale of the whole transform, i.e. when you're exporting model with FBX All or All Local). Really annoying and can't figure out how to fix it

Issue is still persisting for my avatars. Its not a huge jitter, but like the others recorded its a small rumble. Makes skirts and coats look shaky. My projects are on sdk version 3.8.2

Ran into this issue again - collision turned off, ignore child physbones turned on. No collider present, but acts like its colliding with something

Do you see the same jitter in the client, or just in an SDK project?

Prefab used for the test gifs: (Just remove .txt from the extension)

Can confirm: