After also testing with a GPS watch, it just seems to be general inaccuracy as a result of cloud cover and trees. Although there are things that can be done with the phone to help, it seems that in poor conditions there are limits. The GPS watch can also be switched to Glosnass and other sources as well simultaneously but the rate at which it eats battery, I didn’t bother. So it looks like I’m as good as I’m going to get.
