The scouting thing is a bug that is fixed in the next one, yeah.
As for your sudden crash in citizens, there are a couple of things:
1. You have massive crime showing up.
2. The deaths were from that (hover to see).
3. Your crime rate was astronomical because of a huge shortfall in meals that you had for some reason. Not sure why you had so many hungry citizens, but hey -- now they're all dead!
Ahem.
Changes in for next version:
* Some adjustments to crime severities at higher populations:
** The amount of crime per unit of littered trash is no longer so increasingly dire as your population goes up. It does get worse, but not so incredibly bad.
** The amount of crime per shut down building is really REALLY toned down.
** The progression of crime from unclaimed bodies also is now a lot less severe.
** The crime for unemployment has a lower threshold now, as well as scaling lower.
** The crime for hungry citizens was absolutely off the charts nuts after you passed 4200 citizens in particular. It's now a lot more reasonable all the way through.
** Same deal for homeless.