If the Akonadi server is not running when the AkonadiTray restoration tool attempts to restore from a backup, it will fail with the wholly uninformative error of "The restore process ended unexpectedly. Please report a bug, so we can find out what the cause is." Terminal output: ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/home/user/.local/share/akonadi/socket-host/mysql.socket' (2) akonaditray(14806) Restore::restore: Executed: "/usr/bin/mysql" ("--socket=/home/user/.local/share/akonadi/socket-host/mysql.socket", "--database=akonadi", "</tmp/kde-user/akonadiVZMB7p/db/database.sql") Result: 1 What should happen: AkonadiTray should check if the server is running, if not, it should automatically start it in the background, and not run the actual restoration process until the server is started. Additionally, (yes, this is out of scope) the vague error messages should be replaced with something which allows a user to easily see & copy the output, which should make for better bug reports. (no terminal digging, hooray!)
This bug has only been reported for versions older than KDEPIM 4.14 (at most akonadi-1.3). Can anyone tell if this bug still present? If noone confirms this bug for a recent version of akonadi (part of KDE Applications 15.08 or later), it gets closed in about three months.
Just as announced in my last comment, I close this bug. If you encounter it again in a recent version (at least 5.0 aka 15.08), please open a new one unless it already exists. Thank you for all your input.