Retargeting Mixamo In-Place Animation To Epic Skeleton

“Step 7) Upload the Manniquin_NoRoot to Mixamo”

On import to mixamo, my skeleton looks wrong: http://imgur.com/a/Fjua4
i.e. the skeleton seems to be flat on the ground. Any idea what can cause that?
Everything else seems normal, e.g. when I add animations, they work correctly.

Also,

I notice that the imported Mixamo animations seem to have a slightly different alignment / foot placement, than the original mannequin ones, i.e. when placed as a mesh into the level at 0,0,0 the old animations make the mannequin go 2-3cm below the surface. Mixamo ones look fine. I guess the fault lies with the original mannequin animations?