Ally becomes hostile- Wants my protectorate's provinces?

[Lapsed Pacifist]

Just now for some bizarre reason, Russia, my loyal ally, has suddenly become hostile to be due to that troublesome 'Wants your provinces' modifier.

The worst thing though? They don't even want MY provinces.
They want my protectorate, Ethiopia's provinces.
Which are all in Africa.
AND THEY ARE RUSSIA. :angry:
They don't even have a cassus belli or a mission against Ethiopia!

I know allegiances and strategic interests change and all, but couldn't the countries in the game at least break valuable alliances for reasons that actually logical?
I don't suppose there's any way to stop this?

 

[Ultrix Prime]

Interestingly, this happened to me last game wherein I was actually playing Ethiopia. In fact, how can they be your Protectorate? They're Muslim tech now and start with a huge tax and are pretty OP in human hands.

Ethiopia should be vassalizing you!

They could have been your vassal, but in 1.8 since they're Muslim tech, protectoratizing them shouldn't be possible, I don't think.

Anyway, yes, something weird is going on because being Christian (Coptic) Ethiopia I figured I would try and ally Russia to try and balance the Ottmonsters who roflstomped me 3 times. Loe and behold, Russia suddenly started hating me because it wanted my territories out of the blue. There must be some goal or something that's new driving this.