rig / animation / weights completely broken when exported out of blender

[roundsey]

New-ish to both mmd and blender. Model / rig seemed fine in blender, but when I export it as a pmx and put it into pmx editor / re-import it as a pmx in blender it's nothing like the version that runs natively in blender. Video Example right is the version from blender, left is the re-imported pmx model.

[UuuNyaa]

Models that do not strictly follow the rules of MMD Tools will not export correctly.
The model may have elements that differ from the MMD Tools rules.