I've tried numerous boots, converting both with WW and the fitting room.  No matter what options I use, the following happens:

 

WW  - The boot fits well, except for the human figure's foot.  I can make the foot transparent.  But as soon as I bend the boot, the heel stretches as if it's connected to the floor. 

 

Fitting room - The heel disappears, and the boot fits with the foot of the boot at about knee level on the human figure.