Destroyed a kingdom, later a mercenary company joined, now it's not (and can't be) destroyed anymore

[Briansey]

Summary: Two bugs in one. I defeated the Battanians (me being a Khuzait vassal) since they had only a three clans left; I killed the remaining lords, their settlements became mine and on the Encyclopedia it said kingdom destroyed on the right of the Battanian page. The first bug happened: even though the clans were all Battanians, one of them changed their banner color as if they were from a different faction (and they were all dead already so they couldn't have changed factions, and if that happened they'd appear in a different Encyclopedia page and not that one).
Some time afterwards I found out that the Battanians were again at war against us. I thought that was weird since they were gone, so I checked the Encyclopedia again and noticed that somehow the Company of the Golden Boar had joined the destroyed faction. In fact, only one lord of the Company was alive. I killed him and found the second bug: now it doesn't say "destroyed" on the Battania page, so they're perpetually at war even though they don't have any leader, lords or fiefs. Afterwards I destroyed the Western Empire again by killing all their lords, even though they still had a mercenary company hired with one member alive. I understand that you can defeat a kingdom if you kill all non-mercenary clans, but seems inconsistent in these two cases I'm mentioning.
How to Reproduce: destroy a kingdom and wait.
Quest/Settlement Name (if related): none.
Media (Screenshots & Video): Here you can see the different color banner and how it doesn't say kingdom destroyed on the right or above the Battanian banner. Below you can see how the Western Empire did remain destroyed (as it says on the right), even if they had a mercenary lord still alive (they were already with the kingdom before I destroyed it), and now this company can't change factions.

Version: happened today to me, so 1.09
Computer Specs: Irrelevant in this case.

 

[Khan_FR]

How to destroy a clan ? they always come back when you kill there armie and make prisoner, the lord escape 2 or 3 day after his capture ... ( bad english sorry for that). I can't kill theme, they have no castel and turn around my town, kill farmer, and when i fight one , an other escape of the jail .
And there are more faster than me. Can we really kill a faction ? ( i need to destroy south empire)

 

[Briansey]

How to destroy a clan ? they always come back when you kill there armie and make prisoner, the lord escape 2 or 3 day after his capture ... ( bad english sorry for that). I can't kill theme, they have no castel and turn around my town, kill farmer, and when i fight one , an other escape of the jail .
And there are more faster than me. Can we really kill a faction ? ( i need to destroy south empire)

I destroyed those kingdoms by killing every lord. Once you capture them, you select them on the party tab and press the red skull below the name. Then you confirm the execution and they're gone.

 

[Khan_FR]

Tanks, But, how to destroy a kingdom with honnor ? how to increase the time to the jail for the lord ... theys escape all the time, i can't capture all in the same time

 

[BlueFreddyYumYum]

The same happened to me but with the Khuzait. I literally cut the head of all their nobles and minor factions and conquered all their cities and castles until it says they were destroyed but some days later (in game) they were back because a minor faction had joined Khuzait. 2 other minor factions joined their faction later as well. I hunted down all of them and cut their head but the Khuzait are still not destroyed even though there is no one alive and their strenght is at 0.... This is frustrating lol