Custom made mesh from mixamo skeleton problems

Hi, I made myself a very basic stickman mesh in Blender, and imported it to Mixamo to get a proper skeleton for it.
After downloading, the custom amination is fine with it, but when I want to reuse the existing mannequin and retarget the skeleton for it (after making sure the bones match), I run into a problem with the legs.
Somehow the legs are all squashed, and I’ve no idea why, or how to correct it. It ends up looking like this picture.
Anyone have any idea on how I can correct this, as I really want to use this or similar to avoid legal stuff.
Thanks