After working successfully for 18 months, I now get many drops in my internal GPS. Even sitting outside in the garden with a perfect view of the sky, GPS Status and Google Maps give perfect results, but Skydemon is 'Waiting for location' more than half of the time. This problem started about 6 weeks ago. 

Using SD 3.0.7.19226 on Android 4.4.4

Problem solved! Using 'Bluetooth GPS Provider' app for Android instead of 'Bluetooth GPS' solved the problem. Groundspeed and Course over ground are now correctly transmitted to Skydemon on Nexus. GNS 2000 works fine now.