Thanks for your comments. At one time I had the same problem with the autopilot that you describe. But updating the D-180 software fixed it. After that the D-180 worked fine with the GPS496.
Now with the 496 replaced by the iFly 740, the GPS serial data is sent to the D-180 for the first several minutes of a flight. Then it just stops for the remainder of the short flight. I can tell because the wind arrow disappears and the magenta on the HSI screen disappears too. When I download and analyze the Dynon data log after the flight, the GPS-derived date changes to zeros at the same point where the wind arrow and magenta disappeared. No bad wire connections were found.