Hello.
I am using blender 2.8 with Source tools version 3.1.0.
I made a bunch of animations before and every now and then i get this error where bone movement when using SMD is broken and some bone jitter about. This jitter appears when exporting the SMD, as it is present right after i export the SMD.

Here's a gif of how it should look: https://i.imgur.com/yQE9DH5.mp4
Here's a gif of how it really looks: https://i.imgur.com/mOAWHIR.mp4
Here is my blend file of that sequence: https://drive.google.com/file/d/1cu3fD3L3hfpb0pmg2ptAZHgPfnw7QSsg/view?usp=sharing

Does anyone know why this is happening, or better yet, how to fix it?

Ps: Using DMX as an alternative doesn't quite work. Smooth movement makes the bones pop around sometimes, which looks bad.
Edit: now using blender 2.90.1, no change