The ladders themselves seem to work just fine. You can literally shove a soldier onto the ladder and if their feet touch it, they will climb up. The interaction between the ladder and ai agent seems good.
The problem that I have observed is one of queuing. The men standing about the ladders are waiting for something. You can often run through them, bumping them around. This sometimes stimulates a few of them to climb the ladders. Giving them orders to charge doesn't seem to do anything.
Whatever type of "controller" is running the siege is not giving proper instruction to the soldiers that should be climbing the ladders. This leaves most of them in a perpetual wait state. They are given instructions to run to the ladders, but only some of them seem to get the instruction to begin climbing.
The ladder climbing is better in some scenes. There are two battanian castles and the town of Revyl where non-tower ladder climbing seems to work better. Some of the ladder climbing issues are scene specific.
Those siege towers are pretty crazy. In one siege, my men would not climb up the siege ladders, but the defenders began climbing DOWN the ladders. I stood at the bottom of the tower, shooting the defenders in the ass as they attempted to climb down. And they were using all three ladders!
This seems like it should be easily fixable. I would make the ladder and siege towers themselves give climb-up instructions to the men nearest their base. The soldiers have no trouble getting to the ladders, they just need some help on deciding when to start climbing.
Sometimes they are waiting for a command, Sometimes they are attempting to go somewhere, and it is because of the collisions around the ladder, and how the troops work together with the same command.
For example, say you also have 50 troops with the same command to attack the final two units on the battlefield. They all swarm towards the units all attempting to attack.
Saying to 50 units, attack two units, can sometimes make those two units harder to hit, because of the collisions, and sometimes those two units, at first get more attacks in, before finally they do go down, because of the collisions. Battle is not exactly the swan lake of real battle.
Thus, there is an issue
1/ The program loop of command - Some units are not trying to climb the ladders at all in the grounded base ladder
--- The only time that they do try to climb again, is when the defender knocks the ladder down, and they get a climb order when the ladder is put to the wall again
2/ Siege tower - Collisions of units, that you as the player can bump the units up the siege ladder
And obviously, the programmer is having problems solving this, or else it would be solved. So we are then waiting on the programmer to solve his problem. Perhaps another programmer would solve it more quickly. Yet I am not in charge of human resources at that company, or how they do things.
I can only imagine, eventually, they will solve their problem, or the programmer having the issue, will solve it.