What is going on with ballista\cannon towers? I was preparing to defend as Byzantine Empire the citadel in Adana against the Mongols and in the battle the cannon towers were spitting arrows!

I've read somewhere that ballista towers work as cannon towers and vice versa, (and actually seen it in game playing as Venice and defending Jerusalem) so I reloaded replaced the cannon towers with ballista towers and the result is the same: they only fire arrows/ballistas.

The graphics are different in the battle: ballista towers have rectangular openings, cannon towers have round ones. But I can see neither ballistas or cannons protruding.

Is this buggy only for the Byzantines? Do they really have cannon towers when they don't have cannons as units apart from bombards?

Cannon/Ballista towers have bugs. Playing as Venice Ballistas were acting as cannons in Jerusalem, playing as Byzantines I don't have cannon towers in Adana. I am not sure how big the problem is for others but for me it destroyed my campaign.