I’m not sure if this is a bug, or if is a geographical feature. There are some horizontal lines that render on the map as national borders at certain zoom levels. See the attached screen capture of the area between Anchorage and Fairbanks, Alaska. The lines are approximately at the following latitudes: 62.55363°N, 62.87741°N, 64.74465°N, and wrap around the globe.
None of these are the arctic circle, it renders properly at 66.56°N, and there is no OSM data at these locations. I can’t figure out what these lines might be representing. Perhaps there is some NaturalEarth data for these latitudes, but don’t know how to interrogate it.