Sometimes when the enemy ages up, it doesn’t trigger the message “Player has reached X age” on the screen. This results in the enemy having a big advantage, as they have an army composition/upgrades that we are not ready for. Happens consistently enough for it to be noticeable, about 1/3 games in 2vs2 I would say, but with no concrete number.
Whenever it happens, it doesn’t show the message to both me and my friend. As we both notice the other enemy getting the age up and we both call it out every time, I don’t think it’s us missing it.