Hello,
I’m also looking to solve a similar problem. I experienced GPS glitches with my Navio2 and arducopter 4.0rc1 or 2.
I had a flight today with 4.0 and had a GPS glitch when doing a slight banked rotation.
With 4.0rc1, my Gps antenna was at the end of a long mast and I had heavy vibrations. With a shortened mast, vibration level is better but GPS glitch is still present.
Here is link to the log: https://www.dropbox.com/s/mezpo4hmw927a3b/2019-12-29%2014-34-57.bin?dl=0
There was an EKF failsafe event: it entered a Land sequence (GPS glitch not cleared). I changed flight mode to stabilize and had RC control.