I did not start a 1.27 game so it might be a return to norm of game at release.
Attribution of prizes of war is built on a falsely consensual process.
The King looks at this vassals and tries to satify the most of them (not sure that one man is one vote though, terms of influence might kick in)
Lords have a different perception and expection of what outcomes a war should bring. The more heteroclite the faction, the hardest the equilibrium point is to be found (reversely, this also offers more strategical options as part of the faction will always enjoy what's just happened)
If the King faces a controversial outcome, He solves it by attributing land to himself, frustrating lords at the same time. A ticking bomb.
In the end, some of them grow rival status and are banned. A down spiralling process in weaking the faction.
Managing the dissent is the motivation of the political side of the game.
Adopting a vision of life, trying to gather around it to subvert the benefits of group life to your own benefits.
The way to go is to patch up the faction. You can either work at kicking out troublesome lords in order to clear a majority; bringing in enemy lords with the correct profile in order to strengthen a large minority in the faction; settling quarrels (indicated by wife/husband, probably according to her/his own expectation, perception)
I did not start a 1.27 game so I dont know if your current situation can be patched as at release, a situation could worsen beyond repair.
As Harlaus has attributed much land to himself, weakening the faction by cutting lords from their revenues, I would go for bringing new blood, select lords whose profile will help to clear out a majority. This might lead the king to distribute some of his lands to the new vassals, improving the efficiency of the factions.