@radhoo, the SD card doesn’t go offline every time that I arrive home and put it in place for an upload of offline data, probably in part because I’m aware of it, but the combination of conditions that I mention is consistent.

I ended up buying a few of each of five different types of GPS antennas, totaling ~AU$75, but I haven’t received any of them yet, due to slow shipping from China; some have arrived in Australia now, though.
Also, you haven’t provided any instructions on how to take the Model D apart, as per one of my previous posts:

In the meantime, could you please provide instructions for disassembly, so that I can have a go at mounting the small antenna inside the model D? In particular, disconnecting and reconnecting the screen; as well identifying any items that are particularly fragile or for which special care must be taken.

I must confess that I was beginning to wonder if @radhoo or anyone else still read this thread and was considering not posting anymore since, with no one else participating, it was essentially turning into my blog – so it’s good to see a bit of activity here 🙂