A wall of failure?

Hi all! First, I wanna say that I’m a big fan, and been looking for such a political simulator for ages. Thanks, cliffski!
While some scenarios are pretty easy (Bananistan?), I keep trying and trying with others to no avail. Regardless of random events, I was wondering if it’s possible that the game might become unwinnable right from the start at a given difficulty level? Are there optimal interest, economic volatility and difficulty settings that allows the player to win while still being challenging? Has the feasability of all scenarios been tested with the default settings?