When I play a siege and I try to get my men to climb a big siege tower (the ones that are completely covered in wood and have a small archer slit on top), they go to rush up the ramp but just keep milling around the bottom. The AI has the same problem when they are attacking my walls.

I can somewhat fix it by cancelling their orders and then teling them to run to the wall, or attack another unit, but it's still really annoying and time consuming because I have to do it several times before the whole unit is up.

What I play: Vanilla Rome 1.5. No BI, no Alexander.
Help would be appreciated, thanks.