I've run into this problem a couple times now using Affiinity Designer 1.6.1 where it renders a duplicate set of artboards on zoom in and out. They appear briefly while zooming in and out, then disappear. It seems to be fine after I restart the app. I got into this state as I shut off my Mac without closing Affinity Designer. Then after restarting my Mac, Affinity Designer reopened and I got into this strange state. This also happens sometimes while I am just using the app. I'm running macOS High Sierra 10.13.4 on a Macbook Pro (Retina, Retina 13-inch, Early 2015). 16GB Ram, 2.7 GHz Intel core i5 (Benq SW2700pt external display, via HDMI). See posted video.
affinity_designer_zoom_bug.m4v