The assumption here doesn't hold.
You still have an x-turn deal going with the AI in question.
Almost everything in the game comes as situational. Without a save and more information than you've given us, most of what can get accurately said should sound like "academic free-thinking". I can't tell you exactly what's going on without information from the 'trade' section (which details current x-turn deals) of the trade advisor... either via screenshots or a save.
Yes i understand that assumption doesnt hold 'cos reality proved me different and after 6 turns i anyways have "broken" RoP.
No i dont think i had x-turn deal. I'm pretty sure i cancelled everything and i could also trade with other civs with no additional costs as well, so....
Well i'm sorry if we misunderstood each other, i'm trying to to understand if by given data this should be happenening or not. Not actually trying to find the cause. I mean who knows, maybe i'll upload 2 saves(before and after), screenshots, write poems here and it turns out that its the way it should be happening.... So i am just asking understand whats going on... So as i understand now, it should not be happening.
I'll try to remember next time i have this and get a saves