Why do kingdoms randomly appear inside my realm (empire tier) and become independent without wars?

[Tovarish Leninade]

hello guys!, new to the game. I converted a save from CK3 to EU4 with the glorious roman empire. Did well for a few years but then, to my absolute horror, kingdoms inside my realm started to appear as independent little by little (for example: syria and bulgaria) and basically turned the map into peak border gore. My question is: what are the mechanics behind these kingdoms becoming independent without even needing a war and with just a CB for me to make a painful reconquest core by core?

 

[watchout86]

hello guys!, new to the game. I converted a save from CK3 to EU4 with the glorious roman empire. Did well for a few years but then, to my absolute horror, kingdoms inside my realm started to appear as independent little by little (for example: syria and bulgaria) and basically turned the map into peak border gore. My question is: what are the mechanics behind these kingdoms becoming independent without even needing a war and with just a CB for me to make a painful reconquest core by core?

Did you have rebels holding that land for a long time? Aside from rebels, or peace deals, or accidentally releasing them as vassals... I'm not sure how that would happen.

 

[Tovarish Leninade]

Did you have rebels holding that land for a long time? Aside from rebels, or peace deals, or accidentally releasing them as vassals... I'm not sure how that would happen.

I've had some rebellions inside both kingdoms but I destroyed their armies and recaptured their cities. I'm 100% sure it has nothing to do with peace deals or accidentaly releasing them. In fact, when they became independent a few years had passed since the last war.
I have no idea how one can lose so many territories and only get a pop-up telling me I have a claim on their cores....
forgot to say that the kingdoms that appeared don't have all of their historical territories, just a few of them