PSA: If you release a *historic* vassal that is a higher government rank than you, they now just become independent. And theres nothing you can do.
Was playing Genoa, looking to make some vassals. Fought Aragon, won, took the Mallorca province. After the war, released historic vassal: Kingdom of Mallorca. To my surprise, a few days later they were just completely independent. No warning, no event, no notification. Tried the same thing with Sicily and Cypress, same results
I am still not sure if this is intended or a bug. But either way, it is certainly new after the 1.2 update. It also completely ruined my strategy because I suddenly can't make effective vassals like I want.
Edit to add: theres an interesting discussion to be had about whether releasing a subject just to use their cores should be a valid strategy or not (I mostly think it IS valid, but I can see the other side of the argument too). But either way... If like my capital city alone (Genoa) has a greater population than an entire other country (Mallorca, Cypress, etc), there is absolutely no reason I shouldn't be allowed to vassalize that country in some way