Why does it not mirror properly?

Hey guys, this is supposed to be a box. I made 1/4 of it and am not trying to complete it by mirroring it, but it doesn't work. It always mirrors it across the xy plane or xz, but not across the yx, or across any of the faces. It's not a display error or lag, it just doesn't work, it also won't work through multi transform.

I actually successfully mirrored it before, then I deleted the mirroring changed some things and now it doesnt work anymore. Anybody got clue why? Other objects it the file mirror just fine.

Done in freecad 1.0.