The GPS is unable to get lock, or excessively slow, when the signal is weak. Not very weak, just somewhat weak. Side-by-side the Android 10iii is far better.
The SFOS 10iii, has no trouble finding sats (GPSInfo), and does so as fast or faster than Android. But it is then unable or slow to turn that into position lock.
My XA2 was completely useless. This is not better, but inadequate as it is still unable to get lock at all, in places that Android phones (both Quallcomm and Mediatek) can lock within 30secs.
To me, this seems to be the same issue that the XA2 had (and not an X10iii specific one): There are enough “green” sats, but it takes a long time to lock or fails to lock.
It also appears that compared to Android, it may not cache the ephemeris/almanac, so it has to get them everytime it starts acquire. I have not noticed the issue that the XA2 had, of occaisionally starting up reporting a position that was a few weeks old.
My tests that I have posted were a bit varied:
first try and second try and third try
Note that the SUPL/MLS/AGPS suggestions are quite irrelevant to me. I require that phone to work in the bush where there is absolutely no cell coverage.
I’m also not convinced that they will make any difference, as the phone should know exactly where it was when the GPS last had lock (i.e. here at home) but this does not help it find lock next time I test 5 mins later, in the exact same place. The starting position, almanac and ephemeris should all still be valid.
edit: @vige requested the Android GPS app I used: HamGPS (play store)