I saw it mentioned before either here or on the steam page, but there's a weird prestige issue with the Imperial government form. Along with that, it also bugs out Merchant Republics; whenever a house gets created, it's created as Imperial gov rather than Merchant Republic, so a day later they get removed as a patrician. This can get out of hand with courtier numbers (one of the MRs I had was over 1000 court members, which is werid, cause they are the only ones I didn't get a notification about a new house rising up for them) and seems to always get out of hand money wise (every MR under me and/or the Byzantine was at least 50k gold, highest was Pisa I think with like 120k).
I think this is where the prestige issue comes in too, because there have been times where I get hit with an absurd negative prestige amount out of nowhere. Like, maybe when the Imperial government form trickles down to your vassals and your vassals vassals, you are paying prestige? Cause I got hit once with over -250k (give or take) prestige once, probably from the MR bug. And even outside of that, I remember on the steam page or something, someone said the Byzantines/Imperial gov. get hit with a random -4000 prestige, which iirc is the cost of the Imperial law change. IDK tho.
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Oh yeah, I know someone mentioned the laws "sticking". I don't know for sure or anything, but maybe it could be something to do with the Primary title's application of laws to others? Like, my primary title (Empire) has Free Inheritance. I made a secondary title (Kingdom) have Regulated Inheritance. I'm pretty sure at the time of doing it it didn't stick (so the latter only had Regulated), but either 'automatically' at some point in that session (like how passing the Imperial law at the bottom will automatically change your government type after a few days) or when I loaded up the save again, the secondary title had Free and Regulated.