Most of my problems with the game occurred in battle, except for the notorious late-game, gradually worsening lag/stutter/crash that stopped me in T140. Only able to exit via Ctl/Alt/Delete > task mgr > close app. Unable to re-load. Very frustrating after putting up with all of the slow play and crashes for nearly 50 turns. This is well documented by others.

1) It was unclear to me how to employ reinforcement/support units on the battle screen. I realized that you could pull them into the battle after the engagement started, but it didn't seem like I was always allowed to involve each of them. I would like to be notified how to use them by clicking on or hovering over the unit.

2) When a battle is about to begin, I work hard to get terrain advantages, but random deployment often removes every unit from the selected hex. Also no clear way to alter the randomly generated deployment of my units. I hate when my ranged units are put right up front in the battle line.

3) No explanation for it, often unable to take or engage an outpost or city during a war when the opposing units are nowhere to be found. My units say "no way" or "can't do it". 

4) It is not always apparent which units will be involved in the battle. The instance that I refer to was when I was trying to eliminate the final units of an AI that were in 2 nearby areas. One stack of 4 and a singleton about 5 hexes distant. I had the 4-stack completely surrounded and the nearby singleton with 3 of my units adjacent. The 2 groups were not contiguous, 1 hex separated the closest of my units in the 2 groups. When I clicked to attack the 4-stack it used the units around the singleton as reinforcement/support and took away their movement for the attack they were supposed to make. Worse yet, I could only kill 1 unit in the 4 stack at a time. The AI was allowed to disengage from the battle without running away (they were surrounded). It took 4 game turns to kill them, not 4 rounds in the battle. They were 1 shot kills. In the meantime I had to chase down this singleton again because the singleton slipped away because my units lost all of their movement 

5) Finally, and possibly the most annoying bug of them all, when my units engage an adjacent foe, but are forced to redirect for 2-3 turns worth of travel to engage AI. There is no clear cut terrain differential that would prevent them from the immediate attack, but worse yet, I am not notified of the circuitous route until after they take off. Hate when that happens!!!!