I'm playing a game where we've reached endgame, it's around 1995 (turn 275) right now but since maybe the 1700's I've had a bug where I cannot receive or send any trade offers. Or rather, I can send and receive them, but the ones I send are cancelled with a "Deal no longer valid" once my next turn comes up and the same thing happens if I try to accept one sent to me.
Needless to say, it's rather annoying to have this handicap in a game that I've invested almost 300 days in :/