OVROverlayCanvas breaking at runtime

I decided to try out OVROverlayCanvas with a small test, and sure enough, it turned my fuzzy UI into crisp, perfect quality UI.  So I made the necessary changes across the entirety of the project.  Things were looking great in the build.  Then, for no particular reason I can find, every instance of OVROverlayCanvas across multiple scenes broke. They went from looking like this:

...to looking like this (at runtime)

Between working and not working, the scene from which I took the above screenshots, has had no changes at all.  Any suggestions?  I’m working in Unity 6.3.1f1, with Meta XR SDK v83.0.1