Ahhhhh, I see it now.
It tricks the eyes doesn't it?
The blade tapers, but the scabbard can't!
I suspect the only "way around it" is to extend the straight arm of the quillion out farther before breaking it over.
Either that, or set the scabbard up for "edge up" carry, and cut it so the spine of the blade lays flat. This would clearance the top one, and of course the bottom one is bent back towards the pommel.