I've noticed that diplomacy is very unreliable in this game and i don't know if this is a bug or intended problem.
For example non-aggression pacts. They seem to not be valued at all by any faction whatsoever. And I understand ceratin factions have 'unreliable' trait and you should expect them not valuing such agreement, but this happens over and over again with essentially all factions. They will declare war on you even though you are liked by them and have a non-aggression pact (sometimes even combined with military accsess) and they don't have any 'negative' diplomatic traits that would suggest acting like that.
Another example is war declaration. The balance of power bar seems meaningless because even though you have 50+ settlements factions with 1 or 2 settlements will declare war on you. And a lot of the times they aren't even your neighbours either. Completely neutral factions across the entire map with terrible balance of power declare war on you.
Another example is vassalage system. Factions you vassaled by conquering their last city or otherwise will seceede from you very soon or sometimes in the very next turn because they refuse to join you in a war some other faction declared on you. And they don't have 'unreliable' trait. I've had this example with my army still standing next to the vassaled faction's only city (vassaled last turn). I would think vassalage pact would be even more reliable than military alliance. Or that factions would consider seceeding only when they have grown in strenght enough to challenge you.
It seems to me diplomatic agreements are valued way to little or sometimes even not at all by NPC factions in this game and that there should be more 'stability' in diplomacy. But than again maybe this is all intended as a very volatile time?