https://forum.inaturalist.org/t/iphone-app-does-not-use-time-and-location-stamp-in-photo-exif/2581/5
This happens to me from time to time. The issue seems to be the phone not properly putting the coordinates in and instead it “estimates” them based on the points it has for your phone before and after. When I look at the metadata, there’s a locality, but it’s labeled as estimated.
True, this is indeed part of the problem. But also when a photo is geotagged is does not work the first day but when you retry it another day it works fine.
It seems you do not see it in the app but on iNaturalist it has a (wrong) location.