I have a fun story relating to this. I'll start from the beginning. I was the king of Leon (Alfonso IV?) at the 1066 start. I had one daughter Sancha by Matilda of Tuscany. Matilda died so I remarried. Can't remember who. I had an imbecile son. While this happened I assassinated my brothers for Castille and Leon. I hoped that I'd get another son and that this one would die but no. I died in battle and my imbecile son inherited the realm. He died quickly though, and his sister the duchess of Tuscany inherited! Yay! She reigned for a good 60 years and took back Iberia basically. She outlived her children so her grandson was her heir. She created the Empire of Hispania in her mid 70s.
And that's when I ran into the problem described in the OP. it was Gavelkins even though all my 6 kingdom titles were elective. And because of that, for some reason my Empire is set to be inherited by my Piast grandson (the son of my daughter, my oldest child) the king of Poland. This has additionally reset all my elective monarchies who previously backed my Jimena grandson. The King of Poland is now the heir for all but one, with a total of 0 votes.
My response has been save/reloading until my queen has lived the ten years to change the inheritance laws of the empire and made attempts to assassinate the King of Poland. I maimed him and have made it to the age of 85. Unfortunately two of my vassals are fighting wars with each other even though I have medium crown authority everywhere. And that kind of war basically never ends. So. I just have to kill the King of Poland. If this was an intentional change then I feel it should have a warning when you create a new title that it will be Gavelkind and not whatever your primary titles succession is.
And that's when I ran into the problem described in the OP. it was Gavelkins even though all my 6 kingdom titles were elective. And because of that, for some reason my Empire is set to be inherited by my Piast grandson (the son of my daughter, my oldest child) the king of Poland. This has additionally reset all my elective monarchies who previously backed my Jimena grandson. The King of Poland is now the heir for all but one, with a total of 0 votes.
My response has been save/reloading until my queen has lived the ten years to change the inheritance laws of the empire and made attempts to assassinate the King of Poland. I maimed him and have made it to the age of 85. Unfortunately two of my vassals are fighting wars with each other even though I have medium crown authority everywhere. And that kind of war basically never ends. So. I just have to kill the King of Poland. If this was an intentional change then I feel it should have a warning when you create a new title that it will be Gavelkind and not whatever your primary titles succession is.