I had two problems with sources when I upgraded from FTM 16 to FTM 2010. I am now on FTM 2014. The first problem was converting my sources to the FTM templates. This took considerable effort but I think it was worth it. My FTM 16 sources all were imported to 2014 using the basic template. It is not necessary to change them if you don’t want to.
The second problem was not really a problem. Like place names, I found that I had multiple names for some of my sources. I was able to consolidate them into one correct source. The way FTM 2014 handles sources makes it easy to make sure I locate and use the correct source name.