I had the exact same issue. Some days were better than others, but usually the wifi was unusable. Android auto worked sometimes, but it was almost unusable. What worked for me: (1) Removed the back-cover. (2) Gave all(6 in total) back-cover connectors a slight bend upwards very carefully to give better contact towards the back cover (3) Using isopropanol: cleaned the connectors on the phone and the metal surfaces on the back cover (4) Reassembled Directly after startup I got strong WiFi signal, I'm so happy I even tried! I hope this helps someone out there!