Updating an app from previous (0.8) Rift libraries to current (1.17) libraries causes screen flicker

I've updated from 0.8 to 1.17, rewritten for the texture swap chain, etc.. but my application now flickers constantly while running. Any ideas what might cause this?

Hardware is a GEForce 1060 w/ 6 Gb, i7-6700 @ 2.6 Ghz, 16 Gb RAM.. no reason there should be any drop in framerates or anything.