I've skimmed through the thread, and I didn't see this, but if it's already been addressed, then I deeply apologize!
When I trade someone, and then they leave the room without accepting, I cannot trade them again unless I reload. It works just fine if they send me a trade request, but as I stated, I need to reload before I can send them a trade request for the rest of my session.
I've had this happen to people trading me as well, and then they send me the request I'm on the map, then I leave, then they're trapped in the same way for the rest of their session.
There are definitely work arounds, but I just thought I'd mention it since it's happened to me a few times.