This is interesting. Yesterday, I reported a different aspect of the issue, that the map wasn’t zoomed / centered: https://forum.inaturalist.org/t/observations-map-doesnt-reliably-zoom-to-place-so-markers-can-be-seen/38393
Then @pisum pointed me at this issue which is probably the same one. So I tried the link above, and the first time the map had no markers and showed the whole world. The second time the map was zoomed, but panned to the wrong location, like it executes two steps: first, the zoom (which it completes) and then the pan (which it fails to complete, leaving it in the Atlantic):
Now I don’t know if this is two issues or one: zoom and/or pan not being performed vs. no markers on map.