I had vassalized the Franks

The achemid persinas then vassalise them

On the diplomacy circles at the top ,the Franks have a pink circle (thats normal)

if I hover my mouse over the Achemid persians at the top, it says they are leige of the franks

but if I go in the diplomacy screen withe the franks

-a) It is the screen where I can grant freedom, or go to war

-b) but on the sidebar, it says they are vassal to me and the A.Persians

I dont get their tribute as gold income

Then I clicked multiple times the grant freedom button, looked at the treaties screen and all treaties in humanking were displayed (the normal, vassal, and alliance ones)

Closed the screen

I cant get any other screen to come (science, influence, etc)

saved game

the game crashed

On a sidenote, I think that to steal my vassal, the empire wanting to do that must declare war to me too