In a recent game where I was ahead in diplomacy I had other civs requesting a certain tech trade. I usually decline since I want to see what they have and if I can make a better deal.
When the other techs become visible I will make an offer that is better for me. In this game they would refuse the trade and if I then offer them what they asked for in the first place they refuse. I can keep playing around with it and can usually wind up with a pretty good trade but this seems like a bug based on my previous experience that you can always come back to what they asked for to start with.
I also check the relations screen and there has been no reduction in relationship. There has never been an irritation factor with haggling so I'm not understanding the refusal of original terms