Any biplane flying wings after 1914? Were any biplane flying wings built and flown after the 1912-1914 variants of the Dunne D.8? If not, why?

Wikipedia mentions merely that this type was too stable and insufficiently controllable, but that's not inherent to this layout.  And the biplane's stiff truss structure remained useful for the next half decade.
OK, I found one, from a friend's suggestion about hang gliders.  The late 1970's UFM Easy Riser, initially a go-kart engine strapped to a foot-launched hang glider, the "first ultralight."
But this is even more Octave Chanutesque than the 1912 Dunne!  Are there any, shall we say, nonprimitive models?  If not, why?