I ask because on my fresh 3.4 install I cannot get ES to detect the NES/FC30 Pro at all. When I rolled it back to 3.3 I had the same issue until I updated ES from the Retropie Setup menu. Then ES would detect the gamepads and they would be configured (even with the udev driver, no editing needed)
So I had a hunch this was the issue in 3.4 as well. But when I did a fresh install of 3.4, uodated the setup script then uodated ES, it did not delete the input configuration. My USB gamepad was still configured and it still would not recognize the 8bitdo pads.