1. Get the population of a city close enough to its next level population threshold.
2. Disband an army, such that the army population is added to target city. Within the same turn, repeat until target city reaches or crosses the population threshold.
3. Instead of getting the city level up bonus selection dialog, only the level up sound effect plays. It appears that the bonus improvement is lost forever?
I've had the same thing happen with Magnar or the Dead DLC faction when population is transferred to the nearest city as a result of winning a battle (or razing a city).
Any thoughts on this?