Hi,everyone,
I was just about to start a new post with the same problems, when I found this one. I have exactly the same issue with 3 units-2 Garmin 2599 and one Drivesmart 50. I have tried almost everything suggested here even before reading it. Unfortunately with no success. So far these units are only good for spare parts - screen and battery. I can only express my gratitude to all who suggested different solutions here and especially to Butters and Boki who have helped me in person many times.