Disappearing treaties... bug?

[Nitram Draw]

I don't think there is anything like that. In fact the whole Politics and Anger is wierd.
Some races get angry if you have colonies on planets they can see. When you enter into a partnership they can see all your colonies and get pissed real fast. Some get mad over their enemies colonies. Some don't get mad about colonies at all.
It is very common to get a Partnership treaty and have them be brotherly toward you then 2-3 turns later the treaty is broken and they are murderous. Strange eh.