I don't think you have taken in the fact that the Pi3 uses more power than the Pi2. Stuff that worked with the Pi2 might still give problems on the Pi3. Have you measured the 5V line voltage on the board? Is the power light flickering? Is your PSU and cable capable of 2.5A and maintaining 5V at the Pi? As I said before, don't waste time looking for other problems until you have eliminated power issues.