Question Problem with Avatars between 2019.4 and 2020.2

I am trying to set up some animations to work with root motion and IK.

I was using the mixamo ones, which are not set up properly for root motion in games, so ran them through a blender converting tool to fix this. Previously I had to use the generic avatar because the humanoid one would bug out.

Now that I want IK, i need to switch these over to a humanoid avatar.

The idea that I understand is each anim should use "copy from another avatar" and that avatar under configure should be "forced into Tpose" from what Ive read online/unity learn.

However, in 2019.4 the LTS I get a bunch of errors when trying to "copy from another avatar" OR "create from this model".



I asked someone to give it a try , and they upgraded the project to 2020.2 and there's no errors on this version. I can even copy from another avatar like I wanted.





Does anyone have any idea whats going on??
In both versions I am losing some rotation control between attack combinations, and in the 2019.4 with the bugged one , I will fall through the floor despite having bake for Y enabled.

 

for anyone that runs into this dreadful bug,
the solution is to (one at a time, cant do in bulk or doesnt work)

Change each rig type to NONE, then back to humanoid. (**changing from generic to humanoid doesnt work, only NONE)
This gets rid of the import warnings,
however I am still having new root motion problems with humanoid, despite trying every variation of baking.