My iPhone 6 has issues lately: 1) bad GPS location service, off at least 100 yards; 2) poor blue tooth connection, work only within 4-5 feet; 3) wifi connection only works for 5 mHz, can connect to 2.4 mHz wifi, but only works within 4 feet distance from the router.
Found this thread days ago, ordered a Wi-Fi Antenna Flex Cable Ribbon from ebay ($3.50) and a simple iPhone tool set ($6), following the steps in the link provided above. In less than an hour, all issues are gone!!! Many thanks to everyone who share the great information!!!
An observation: the old Wi-Fi Antenna Flex Cable Ribbon doesn't seem to have any damage. I doubt why a replacement of a new antenna works just fine... However, I found the insulation material on the bottom of the phone at the upper left corner underneath the antenna connector seems to be damaged (could be caused by dropping of a iPhone). To avoid any complication, I put a small piece of electrical tape on each of the two connector heads. I am wondering if a NEW antenna is needed. Repairing the insulation material damage could fix the issues just fine. :)