Is this a bug? - v1.22

[Splitter]

I had an agreement with another civ for 20 turns, i gave him iron and he gave me gold per turn. However at the end of this, the renegotiate window popped up with only him offering his gold per turn in exchange for nothing. I refused thinking it was a one off bug and he was trying to get tech but when i looked under the active trades i was still giving him iron (with no time limit next to it). After cancelling this "agreement" he instantly went to war with me and was subsequently introduced to my tanks.
However, is this a bug or some sort of "feature" im unaware of?
Thanks

 

[ReZurrecti0n]

Has a similar problem with that once before... I would think though that the civilization found iron on thier own, so when the deal comes to a end, it always comes back up except this time they don't need the iron anymore, but still offer the gold per turn. Sounds like it would be a bug of some sort, but I am not sure if this happened for when I switched over to 1.22 or not, I don't exactly remember... As for going to war with you, maybe they were trying to monopoly all iron sources? Hehe, I dunno...