One other thing that worked for me, using fbx exported from Cinema 4D, I’d parented the mesh and rig to a null (for being tidy). All scale was set to default 1, until I unparented from the null, and the root bone scale then reset to 100. I think this is because I added the root bone after I’d already frozen the scale transform of the null. So to fix this I unparented the hips/pelvis from the root, froze the scale transformations on the root, then reparented. Exported without the null. All works now.