As of the last few months (not sure exactly) I have had an error which is "We are sorry, aconadi_control has closed unexpectedly". This occurs about 50% of the time after a reboot and immediately upon logging on. I have re-installed all packages I could find with "akonadi" in the name, I have deleted all instances in my home with "akonadi" in the name, hoping to restore the default. While this did not work, the establishing of a testing user does not appear to have this problem. Google does show similar, but I have been unable to resolve anything from there.
Any thoughts appreciated and of course I will provide any further info requested.