I am also running into this problem. Was a solution ever found to resolve this?

Greetings, I managed to get the body joints to follow the robot's rotation by rotating each of the modelTransform vectors by the bodyAnchor's rotation. I.e change let position = bodyPosition + simd_make_float3(transform.columns.3) to let position = bodyPosition + bodyOrientation.act(simd_make_float3(transform.columns.3))