I don't know if anyone has entered it already, but I encountered two bugs, when I was playing as the Mayans. One gamebreaking and the other one ... weird.
Sadly I didn't think of taking screenshots, but I will, should I encounter them again.
At some point the Mongolians invaded me, when I was moving into Mexico to steal some clay from the Aztecs, which is an event that, to my humble knowledge, cannot be found in the big book of history.
Also, when I failed my third historical goal, the pop-up message telling me this wouldn't want to go away, effectively ending this playthrough.
Apart from random crashes, for which I cannot pinpoint the reason, that is all for now.