WD MCH mobile app sync is just based on Syncthing, but without all the features opened to users. This ‘reset database’ is what Syncthing sometimes needs when it encounters an error, which may be what is happening. There is probably nothing a MCH user can do other than clear cache or reinstall the mobile app and/or delete sync folder on the MCH. Do a backup of the sync folder first of course if needed.
5.6. Troubleshooting
Some times you may encounter database error and Syncthing will refuse to sync the files between devices. In such cases, you can forcibly rescan files and resync the database using the following command:
$ syncthing -reset-database
