After a few years and mobile device generations the state of my address book was rather frustrating: Starting with Nokia Symbian S60 (SyncML) over to early Android (using Backups), on to BlackBerry 10 (Card/CalDAV backend) and ultimately back to Android (using a sync app) has introduced numerous duplications and invisible character additions by the respective address book apps (the Samsung Contacts app being the worst).
Following a little mishap with the DAVdroid app on my Fire HDX Android tablet, I ended up with a lot of duplicate contacts in my CardDAV account. Upon closer inspection I then noticed, that in the process of copying the contacts from the local contact store (on my Blackberry smartphone) to the CardDAV account, certain contact details had been lost and spurious characters (like spaces and question marks) introduced.
The follwing articles were of much use when switching this weblog from the no longer maintained Nucleus to Mezzanine, a modern blog and content management system, based on the Django web application framework and Python:
As described in my earlier post, it is wise to create regular backups of your apps and data to SD card.