iPhone 6 - same issue for me, think it was fine in August and September and now location services is only using phone masts as far as I can tell. My son also has an iphone 6 and his is fine, we both have the latest iOS and mine has been factory reset twice. I also replaced the wifi\bluetooth\GPS antenna. After an incredible amount of time on the phone Apple said to take it for repair and gave me a couple of approved 3rd party partners as it is an old model. I might admit defeat here.
olson_2x4
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