This is a strange issue.
Since before the weekend I've gained 5 settlers for no apparent reason. I have the same amount of buildings, fields, wells and so on. I still have the same number of free licenses but I have 5 more settlers than I did a week ago.
First it was 3 extra for a few days, then suddenly I had 5 extra yesterday.
The only thing I know of that only takes settlers and no license are wells but I have the exact same amount of wells as I did a week ago, I just replace them as they run out, with an exception of a normal well I had to build for a quest that's ran out and not been replaced since then.
I haven't been able to figure out where these 5 settlers are coming from, that's why I'm posting this as a bug.