Today my Edge 820 crashed when I loaded a course during a ride (detailed description below) which required a hard reset. Interestingly, when I looked into the err_log.txt, I found also a freeze from two weeks ago listed. Back then, the Edge did not wake from standby during a ride which could be fixed by a forced reboot. Also the previous track record was recovered, so everything was fine in that case. Interestingly, for both incidents, the error log lists the error cause 8 (see attachment). So my questions are: What does this error code mean? Are crashes under the mentioned situations known and should these procedures therefore be avoided?
Detailed description of today's crash, maybe it helps evaluate the problem: I had a longer ride (250km) for which I had a course prepared. The course was created as gpx-file at gpsies, then uploaded to garmin connect and transferred to the Edge via Smartphone sync (did that before without problems). When starting in a region I know I usually load the course at a point shortly before I am leaving well-known terrain to save battery (today after 45km). This typically works reasonably well (maybe despite being a little slow). However, today, when the question appears if I wanted to be navigated to the starting point, the screen froze. I had this once before, but then the Edge recovered after a few minutes so I continued riding. Because nothing happened, I stopped and as usual the pause sound appeared. Thus, I thought the Edge was still alive and wanted to continue riding but there was no continue sound so I knew that the Edge eventually crashed. Reboot (10s power button) did not work (when shutting down, a small stripe stayed on the display for about 1s, when booting it stopped on the first screen). Entering debugging mode (Power+Start) still worked, but with a few restrictions. Some checksums just showed "??????????". I could neither run a ROM test nor connect to any ANT device. The timer screen still showed the data of my current ride. So I decided to hard reset (Power+Start+Lap), which worked with all the undesired side effects a hard reset has. There actually was a .bak file for my ride until the crash, but it was empty (0KB).
My connected devices (maybe relevant?): Garmin speed sensor (ANT), Sigma HR sensor (ANT), BePro Favero (ANT), Android Phone with Garmin Connect 4.8 (BT), WLAN disabled, GPS only.