My phone language has almost always been set to English and I've always had my geolocation on for my pictures. A couple of months ago I rearranged the Preferred Language Order to bring Persian to the top, over English, to check something in an app. Then I reverted it to the previous order, English on top.
Note that there's a difference between iPhone Language and Preferred Language Order and Persian is NOT among the supported languages for iPhone Language; I can only add it to the locale list (Preferred Language Order) and if I move it to the top, it'll adapt the locale for the apps that do support it.
Since I did this, the Photos app switched all my previous geolocation tags to Arabic (which is the closest supported language to Persian!)
How can I fix this so that the names appear in English again while the phone language is set to English and those photos were taken in an English speaking country long before I'd changed the language?
I've tried rebooting the phone as suggested here but that did not help. I've also completely removed Persian from the Preferred Language Order list, and nothing has changed.