had an interesting thing happen. not really a bug, so i will share here.
playing as greece, i refused the ottoman flip. their stack attacked immediately and i wasn't quite prepared with units but i had tons of bombards ready. i bombarded the crap out of their stack and while my units were flipping, the new units were also damaged. so a stalemate of low helath units developed. i could heal faster and bring new units in but i didnt want them to flip, so it persisted until they would accept peace.
at this point, they had no cities, since i'd raised anatolia and nothing flipped.
instead of attacking someone else, they opened borders with me and then parked their units in byzantion until the end of the game, never going unstable even though they had no cities.
interesting, i had a previous babylon game in which i made i razed constantinople, the homeless ottomans marched through my open borders, and conquered arabia which they held for a while until eventually collapsing.