2 side cnc milling in aluminium

Ive got this weird problem with my cnc mill. All 2d and 3d operations work fine, but as soon as I need to reposition my stock to another face, the work offset seems to be wrong.
Ive tried zeroing with a zeroing tool on the stock corner, putting it in the end of my vice so there is an easy point to recognize when repositioning my stock. I use mastercam and in both top and bottom wcs Ive set the origin to the corner that I can recognize.

the part is quite simple, rectangular shape with an off center pocket and contour toolpath. the idea is to cut the pocket, do 6/10 of the depth contour, flip it and do 6/10 again.

Can someone help me with this specific problem or just point me in the right direction? Most of the online post are about using a hole that goes trough the part, but this is not an option and in my head the vise should work some way.

attached is the part in step format.

Try re-orienting the origin in the CAM program so it's in the middle of the part, not at the corner. Then whatever edge you indicate off of, the zeros will be half the width (or length, or depth) of the block you're milling your part out of, assuming it's accurately centered in your program. The problem you're running into is that the right front corner you're using as a datum point becomes the left front corner in the flipped part, which isn't necessarily the same thing.