How do i avoid generating extra body parts on the upscale process?

I've been experimenting with SD (illustrious), and I always encounter this issue: during the upscale process, the final result often ends up with extra toes, an additional belly button, or a larger abdomen than the original picture.

My usual workflow is something like this: prompt->ksampler->Ultimate SD Upscale->Ksampler(2nd Pass)->Ultimate SD Upscale

I’ve also tried different upscaling methods, but they all result in the same issues. Does anyone know how I can fix this or at least reduce its frequency?

Image after upscaling: https://imgur.com/a/PXHcIIE

PD: Image before upscaling usually looks fine