ResizeObserver loop gives notebook the shakes

At a very particular content and viewport height, a notebook will shake violently due to the scrollbar toggling constantly. Observable’s frontend code already registers this as a ResizeObserver loop error (encountered on

In the below sceencap (taken in incognito mode, after closing the CTA) the document size toggles between 1045x1251.09 and 1060x1253.44.