Not much to go on, so it's just a guess. One of the parameters, likely Kingdom, was broke by one of the mods. If you have a mod that alters kingdoms in someway or even overrides any of the Helpers.FactionHelper.CanPlayerOfferVassalage, then you should start there. Make a post/comment on the mod's website asking the author to assist you.
Yeah, one thing that made me consider this is that in another game, Battania took Hubyar and set up shop. More power to them!
Yeah, companions in your party (and maybe army?) are all found in the town scene now, rather than them staying in the tavern. I thought that companions always stayed in the tavern, so I suggested to visit the tavern when you enter the town so that you could ask your bodyguard to gather them all in a reasonably quick time. But apparently they are in random places in the town, so if you want your bodyguard to gather your companions to attack an alley, it takes like 3 minutes.
Can’t you just ask the companion who is following you to gather everyone? I thought that works in Vanilla. They are all in the settlement. They just aren’t all following you.
Thanks for the extra info.They affect many things. A generous trader would not be smart. Not sure however. Not tested.
A daring captain might charge without orders.
A wanderer with mercy/honor will complain when you raid or attack villagers. You gain honor by doing village quest where they give you stuff. Like the quest to move their cattle to a settlement.
A calculating commander will not charge at once. He will send in his archers and have them use up all their arrows before attacking. Provoke the enemy cavelry to follow you back to the line and he might charge.
I avoid all with devious. Making a wanderer with devious trait a clan leader is more likely to move to another kingdom.
A cruel commander might not help you in battle, Others will stay closer to you on the campaign map.
A commander with valor is more likely to fight in battles with low odds. We have all seen an army of 300 attack a 500 size army to repeal a siege.
presuming you are on pc (and yes, this doesn't answer your request for a mod. but it is what we have)
campaign.kill_hero <name goes here>
go back to playing.