I think I worked out what the issue is/was with the GPS in my model D. Over the last couple of weeks the GPS antenna cover has become somewhat loose and detached many times; as a result of this it looks like now the antenna cable now has a small section of insulation missing and this may have been contacting the chassis of the D. I flipped the antenna over in the antenna cover, which routes the cable in a slightly different direction and I now receive 9-11 satellites in my car and 5-9 satellites where I charge it – at both of these locations it received zero satellites before I made this discovery.

I was planning to flip the antenna over, when I discovered this issue, because I found that, whilst reception was terrible standing up, it would actually receive a GPS lock when laying on its front – which made little sense. After having rerouted the cable, orientation now makes little difference to the number of satellites received (maybe 1-2 less/more).

Looking at the stats, it took around 16 hours and 15 minutes to upload the 9100 samples from this past weekend (it finished at ~04:43).