Never had a problem with my 800 in its 6 years of use; never any data loss or failure to upload. I use mine a little differently: I put my map and the Garmin file structure on an SD card, so my course, if any, and data are all on the card. The card then goes into a USB card reader for data exchange. I've never plugged the 800 into a computer except for updates. The ride data is transferred from the card to a folder on my desktop and uploaded to various websites from there. I have a permanent repository for all my TCX and FIT files on my desktop. I can swap multi-GB map files simply by putting in a different card.
I realize that sounds a bit anal. An early-adopter software engineer got me doing it, and sure 'nuff, never a problem. At the worst, I could only screw up the card, but never have.
The only Garmin software which I use, other than what's internal to the 800, is Garmin Express. I use RWGPS, TrainingPeaks, and Strava.
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