Thanks for that. So far at least the 820 doesn't crash all the time and dump my ride data like the 810 did - and that is a feature that I can put up with a lot for!
What fw version do you have on 810?
I have 5.00 on mine and no crash for 6000 km ....with TBT active following courses
My great experience with this problem I have now solved. Basically once you’re set up correctly most do the TBT navigation. I have the 810. The fly in the ointment is the preloaded international baseline maps which ain’t worth jack. As soon as you download the Garmin City Navigator Europe NT: UK & Ireland all the problems disappear. It’s obvious really as a full international map will lack 90-95% of the details required for TBT navigation. I did this and downloaded the same route I constructed via Garmin Connect and Strava GPX and TCX (I think the acronyms are correct). All three circuits of the same route worked perfectly for the TBT navigation. Any issues with ANY technology do Google DC Rainmaker he is amazingly detailed on almost everything. Below is the link for the map download. Ensure you get the micro SD NOT the download.
Oh and do invest in the original map not some spurious one as it’s not worth the hassle for saving £15-£20.