Have you tried increasing zone radius? What’s your GPS accuracy like? This issue has been discussed in length over the years. Lots of good info in previous threads.
The link that @tom_l posted above is quite good for fault finding. On your phone, open the Companion App → Settings → Sensors. I get can set how often to update iPhone settings, accuracy. And I can see my exact GPS location updated to the Companion App (and then HA).