Enemy unit safely parked in MY city... Bug?

[Brutus2]

In my current game I'm playing as Rome and I'm at war with the Aztec. His horseman just moved INTO my city even though the city has not been attacked at all and is at full strength. You can see the ranged attack for the city walls activated but I can't target the horseman because it's on the city tile.

He even passed through an Egyptian unit who I have an alliance with to get there.

I also got a notification that the city was under siege because the one horsemen had ZoC of every tile around the city by himself!

I will try to post save file as soon as I get a chance.

Spoiler :

 

[Browd]

Moderator Action: Moved to Bug Reports.

Can you post a save file?

 

[Brutus2]

Save file uploaded. Two bugs here...

1. Enemy horse on same tile as my city Cumae causing the city to be under siege by just the one unit.

2. Legion is eligible for promotion but the promotion button does not appear. Possibly because the "Upgrade to Musketmen" button is in the way? I can't upgrade since I don't have Niter and in the meantime no way to take the promotion that I can see. Oddly I played a few more turns and after making peace the promotion button suddenly appeared.