I started off my GPS usage years ago with a Garmin GPS90 using the integral ariel in a P28R. and yoke mounted.(which I still keep powered up as Back up.)
IIRC it only uses 8 satellites and regularly dropped out around the north norfolk coast above Coltishall.
I then switched to GPS295 still yoke mounted but used the remote ariel at the front of the screen in the P28R.
Never had satellite drop out since, all over S england and halfwaydown France.
But don't know if this is due to greater number of satellites used in GPS 295 (12) or use of remote arial.Worth trying remote arial well up front.
Just my two pennorth
Safe Flying
Cusco