1. In a physx build, pick a skeletal mesh and create/use a physics asset for it that has bodies for the root bone and one or more other bones.
2. Call USkeletalMeshComponent::SweepComponent against it such that the sweep should hit the root bone's shape. This sweep should hit.
3. Now call USkeletalMeshComponent::SweepComponent such that the sweep should hit a different shapet that's not on the root body. This sweep won't hit.
There's no existing public thread on this issue, so head over to AnswerHub just mention UE-112915 in the post.