Planar Reflections facing each other doesn't work

Has anyone had any success having mirrors face each other using planar reflections? I know we can’t get an ‘infinite’ effect, but I’d be happy with it just seeing the other mirror as white or something. Instead there seems to be this weird bug where it will sometimes be black, sometimes be white, and sometimes grab some flat image from a baked cubemap (I think) and move that around perpendicular to the camera. Any thoughts?

Here’s a video of the problem: