Newly acquired vassal does not make peace

[ScribJellydonut]

I'm playing a LAN game with one other person, in which Shaka has asked me to declare war on Bismark. Since Bismark is only one of the two players on the map who isn't Buddhist, and I founded the religion, of course I agree. Some turns later, the apostolic palace, now out of my control, votes to war with Bismark, so everyone on the continent wars with Bismark. A few turns later, Bismark catipulates to Shaka.

A) What is supposed to happen
Everyone who is at war with Bismark makes peace(including the other player), and Bismark becomes a vassal of Shaka. Too easy

B) What actually happens
Everyone but me makes peace with Bismarck. Bismark becomes a vassal of Shaka. I declare war on both Shaka and Bismark. Now everyone in the world hates me and my hopes of a diplomatic victory are shot to hell since now not only does Shaka hate me, but most everyone else dislikes me for "declaring war on their friend"

Has anyone had this happen before? I'm looking for a a workaround(other than reloading my game to 50+ years ago). Oh ya and Bismark won't speak to me when I reload it to the turn just before this happens, so there is no way to make peace with him.

 

[JujuLautre]

As usual, a save would be helpful.

 

[ScribJellydonut]

Ya I ended up backing it up about 20-30 turns on an autosave(long before I even went to war). I thought it would suck that I would suffer a -1 penalty relation for refusing to help him during wartime, but he didn't even ask me to this go around.