In case of the Greek island of Ios the island is not seen, only the streets of this island on the water surface. See: https://en.wikivoyage.org/wiki/Ios.
I made a workaraound putting an area of this island as a map shape on the map to demonstrate the existence of this object in the OSM database.
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| Stalled | None | T302086 Set scap minimum python version to 3.7 | |||
| Resolved | None | T247045 Migrate all of production metal and VMs to Buster or later | |||
| Resolved | hnowlan | T264292 Migrate maps to Buster | |||
| Resolved | BUG REPORT | None | T312751 Geoline never shows up after OSM and Wikidata entries have been updated | ||
| Open | None | T260456 [Maps] Reduce Map Sync Latency with OpenStreetMaps (OSM) | |||
| Resolved | hnowlan | T269582 [OSM] perform imposm3 migration in production | |||
| Open | None | T218097 [Bug] OSM DB degradation during sync as a result of missing features | |||
| Resolved | MSantos | T225592 Missing structures like islands on map server tiles |
History of the relation of Ios (history viewer) has edit comments like "coastline fixes" and "repaired relations", which suggest that coastline of Ios has been broken on several occasions over the past months. So likely it was broken at the time when Wikimedia updated coastline. If I'm not mistaken coastline is updated less often than other map features, so it may take a while till it gets fixed. Unless someone tries to regenerate the area manually (approach mentioned in T159631).
It is well known, that OSM ways and areas could be defective. But they are shown on OpenStreetMap. Maybe more fault-tolerant functions are used at OSM as compared to these of Wikimedia. If a relation is an area maybe the shape can automatically be closed.