I had a city level up (level 2) simultaneously with it being attacked. Three units were in the city at the time. 

When the battle started I only had two units. No city defenders. And a unit I had trained in the city several turns earlier was also missing. 

Lost the battle (obviously) and that missing unit was standing next to the city.

I don't have a save or a screen because I threw in the towel (all the ais ganged up on me). But I wonder if anyone else has seen this? 

Also, might be fixed with the changes to simultaneous turns in the next beta.