Thank you for the feedback!
It's not a bug, it's a feature. :) When you are in VR mode and everything around you is virtual, then you move your avatar through the area, so pressing forward moves the avatar forward. When you are in MR mode, you see the real room you are in, your living room for example, which is not movable, so you stay in place and you are moving the slave inside your room, so pressing up means you push the slave away from you...
By the way, I'm working day and night on a next update, where you can move the chains inside the frame to fixate herin any possible way, and soon you will also be able to change her clothes.