Do you do this on a carpet or a yoga mat of some kind?

Do you do it fast? Try doing it insanely slow (it will be harder, as it uses more muscle, but it may help with the grazed elbows)

After you do it very slow for awhile, if it works in terms of non-grazed elbows, maybe try VERY gradually speeding it up.

Ok, now, I just got on the floor and tried it to see what's happening - my guess is it's not going down to the floor, but coming up where the grazing happens. Yeah, it will be hard to go slow, but if you try it, it might help you see what's happening and to avoid it.

have fun trying, and let us know what works!