Why does BodyScale in custom character scramble animated joints

I have a custom character, it works perfectly fine as R15 or R6. It was imported using the R15 option in the character importer plugin.

I want to use the body scaling tech that R15 supports so I can have creatures of various sizes.

The problem is that when I add a body scale value to the humanoid, all of the animated joints get completely messed up in random directions, and I have no idea what the pattern behind it is.

Has anyone seen this before and solved the issue?
There are numerous instances involved in humanoids and scaling (OriginalSize, OriginalPosition, etc.) but no documentation about any of it.

(The hipheight and scooting is a separate problem that I’m not concerned about right now.)

Well I’ve determined this is caused by non 0,0,0 orientation rig attachments, which is frankly ridiculous.