So I discovered a bug at my expense in an auto-battle vs a human in PBEM… I was using the “Mountain Clan” unit from the Westeros v3 mod and map: https://steamcommunity.com/sharedfiles/filedetails/?id=660725638 but the bug is very likely exactly the same on the base game under certain circumstances.
The Mountain Clan unit has Taunted as a base ability, so it always charges forward to attack enemy units and you can’t control its move. That works fine in “normal” battles.
But I discovered that on siege battle, the unit just doesn’t move at all until there is a breach in the wall/gate!! It seems the game cannot calculate a path to an enemy unit and so it just doesn’t move. That is despite the fact that the Mountain Clan have Wall Climbing so they could actually climb the walls and go attack enemy units!
I guess a quick fix would be to add gates as valid targets. That might cause some issues if one gate has been broken but another is still standing, and the Taunted unit will then uselessly attack the gate. At the same time, cases where it’s really an issue will be rare, because if the closest target is a gate, that probably means the Taunted unit is outside the walls and should indeed attack the gate to enter.
Another fix should be to allow the Taunted unit to plot its course through walls if it has Wall Climbing or something equivalent.
Thanks if you can fix this! For the mod and other similar mods, it would be really useful, because right now these units are strongly handicapped in sieges. For the official game, it might be useful too in some rarer cases where defenders taunt a unit when the gates are not yet broken.