I used to see others having this problem, and I'm having trouble finding those threads now.
With the latest FOTS patch (still playing just Shogun 2), I can't maintain a trade agreement with anyone for more than a turn, if I can even get them to agree. This is around turn 40, so it's way before RD. I had a number of agreements in place and they all stopped within a few turns of one another. I have access to cotton via a single trade node. Playing as the Mori.
I can't figure out what went wrong. Are there any references out there that go through why the AI is refusing to trade? At the very beginning of the game, I also find that some clans won't trade no matter how much I sweeten the deal. Then three turns later, they'll accept it outright. I'm missing something.