It's unlikely that it comes from mounting with top/bottom reversed or from horizontal rotation. Toroids work by making the magnetic field rotate back and forth around the circle of the toroid. Leakage is minimized by having the iron be nearly full circles, with air gaps only at the boundaries of the (typically) wound strip of iron making up the core. This means that the air gap is very widely distributed, not at abrupt boundaries like the ends of the E's in EI transformers, so leakage is generally less and much less orientation sensitive.
I can imagine a poorly built toroid with primary or secondary or both improperly clustered on one side of the circle as opposed to distributed all around the circle that would have worse leakage than a correctly built one, but that would be very unusual and probably hand-made, not machine wound.
There's a good way to test. The amps ought to work, if not be ideal, if you swap the transformers around. Or you could do the old test for leakage we used to do in power supply design - hook a circular loop of wire to a 'scope probe and use it as a mag field sniffer.