I'm new to solidorks and I'm having some issues with creating mates after deriving a part in an assembly.

I'm trying to create a very basic box for my raspberry, I loaded the raspberry and the hat and then constructed the box around it. Now I just want to move the raspberry into the middle of the box (with the USB ports still at the wall but the HDMI and usb-c being away from the wall). But I can't seem to make it happen, when I add distance mate it explodes or simply throws an error. There are no conflicting mates for this. Can somebody help? I added the assembly, the one I'm working on is the julian-box.