Prior to my current trip to Asia, I transferred both the Singapore/Malaysia/etc and Taiwan onto my Edge 840 with firmware 19.22. So on the 840, there were a total of four maps: North America, Central Europe, Singapore/Malaysia/etc, and Taiwan. Two days ago, realizing I no longer needed the Central Europe map, I removed it using Garmin Express (MacOS). The following morning when I went for a ride with a course in Singapore, I was surprised there was no turn-by-turn directions. In fact, the map screen was completely void of anything other than the arrow indicating my position and direction.
In the evening when I connected the device to Garmin Express, I realized it only had the North America map. Thinking that I might have accidentally removed the Asian maps, I attempted to transfer them to the 840 again. But each time when the progress hit about 50%, it would error out. I tried loading just one map at a time but received the same exact error. In the MacOS Finder, I was not able to see any files or folders on the 840. With the Terminal app, I could use the command line to get to the Garmin folder and see the most of the files and folders there but there were about five files with input/output error.
Thinking that there might have been a file system corruption on the 840, I did the reset option which did not clear the error. Garmin customer support suggested removing the North America map - the last remaining map - on the 840, saying I won't need it until I get back to the US. I think he was thinking my 840 had run out of space (it had plenty of space). But turned out, removing the North America map actually fixed what I thought was file system corruption. After removing the map and restarting the 840, I was able to use Finder to access the files and folders, and managed to also transfer the two Asian maps without any issue.
I don't know if it was solely the removal of the North America map that resolved the issue, or it was a combination of resetting the 840 and removal of North America map that did it.
