The logical answer must be the spacers you got did not have a center hole as large as the ones that work without modification. I assume the spacers in question were for your BX.
You must have had to enlarge the hole a bit, to cover a center protrusion that I want to remember exists on the BX hub for some reason, which is not related to hubcentric wheel use.
Just speculation because I am not sure I am remembering correctly on the BX. Not even sure if hub is the correct term. Maybe axle flange is what the piece that the wheel pulls tight against is what it is called?