I've cycled through the list of bones to identify influences and also selected verts on body parts such as the foot to know why the verts are being stretched over to the opposite side as if the Characterization ignores the toe weight paint - Also why in bone edit mode the breast bones are symmetric but in animation and weight paint mode the left breast bone is flipped, what's going on here?? The eyes also seem to be offset (looking at J key view)

It definitely seems to be an issue in the conversion process when imported, Importing a custom Character with duplicated parts for HIK mode maybe creating mesh & weight painting artifacts - again like CC3 did at one point.

The conversion of Characters CC3 to CC3+ used to have a problem in the toes creating the same kind of distortion (I've submitted the issue showing my grizzly bear in the past) - my new CC4 Character is also using CC3 bones, 3sets of CC arms and many hands have been duplicated and are numbered correctly.

Also Once imported the materials are duplicated for as many times there are meshes. For example, if I use 3 meshes, and only 1 material on each mesh, the material list will show 6 materials, if each mesh had two materials, the material list would show 12 materials. The top first set of materials in the list are the original, the rest have no function.

Also because my character is symmetric I am surprised the mesh editor doesn't give me the option to mirror it - I also have the same material/UV layout as a CC3 character. -everything is using symmetry.

I rigged the Character in akeytsu you can test and compare, the program is free, download & use the EDU license, upload blank jpg https://www.nukeygara.com/

1.When you open my akeytsu project, to be able to see/verify the weights and move bones, click on "Paint and check" in the Char Bank window.
2. you can now click on any bone and manipulate it. For example hold "alt" to select multiple parts, try the eyes, hold alt and click on each eye, then click on the circular control gizmo that has red, blue and green.. if you middle mouse click and drag while using the rotate button you will see you can control the eye movement in all directions, click on a single color to move the eyes in a single direction. Press x to reset position. Next try selecting a part that I've shown you looks distorted such as the big toe R (it's the last set of tentacles at the tip. Although I've provided the exported character in FBX, if you want to be absolutely sure you can Select the hierarchy in the Tree window and Export the Character yourself to test.

---------------------------------------------------------------You will see that the weight is painted properly in akeytsu but in CC4 it's distorted and it looks like weight painting wont fix it..

The Chest area also becomes distorted in CC4. Also I have the weights painted properly in the throat and the digestive area as seen in akeytsu but if I make the head tilt back in CC4, the throat area clips through.