Happy to have you visit the Cafe!
To do "trouble shooting", there has to be a few questions:
Just for curiosity, what edition & version are you playing?
1400 habitants (Freemode)
I hope I can take that to mean, you are playing a "random island" rather than a pre-designed scenario.
When you say the "stats have mistakes", you are referencing a page in the Almanac? If so, did you cross check the total on that page to the total in the "Circle Window area (lower right of the screen)?
There are probably only a couple of threads on the topic of large populations, and they only discuss maximum numbers. I can not recall any which discuss population errors in the Almanac. So, frankly it is probable that no one has ever before cared to question the game's bookkeeping on that point - so it is not a documented situation.
Also, there is some limited evidence that the game tends to become unstable when some size parameters are pushed.
Additionally, I have no idea of the sequence in which the engine runs its counts and its updates to totals. It is not beyond possibility that you actually have 49 emigrants who have not yet been posted to the Almanac because, although they have gone to the Port and disappeared, a Freighter has not docked to trigger an update to the vital statistics. (Speculation on my part.)
It seems that way back in the advanced development, it was decided not to artificially limit the population because "game-play" would seldom expand the population beyond the engine's capacity -- so as far as I know there is no internal limit mechanism.
a remediable bug or sth
I don't know what
sth is. There is a bit more to be done to identify your experience - in a single game - as a "bug" rather than just a "sport" error in that game.
That's not much help I know, but it's the best I can do singlehandedly.