freebeer
Actually, now I see them in osm-carto at all near zoom levels save for z15, so perhaps it was a cache issue.
The cycle and transport layers show nowt but I know it can take weeks to appear there.
Humanitarian I cannot view (IPv4/v6 support issue, my problem), but unless that has issues, I think you can mark this as resolved now, and I'll mentally file islands somewhere...
Thanks for your patience; try emptying your browser cache and/or reloading the page if you still see no islands at z13 and above.