Happened to me too, I'm Rhagaea's vassal for 10 years at this point and for unknown reasons i have -59 relation with her (never declared war on my own and I haven't raided villages, if that has anything to do with it). At one point i had -71 relation with her without knowing why, I feel that we need a tooltip on the relations that gives us information which event or what causes that current relation with the character/ clan. I gave her the dragon banner and the relation did not change...