Please verify suspicion.

[Randallw]

There shouldn't be duplicate sets as the shipsets are built into the mod. It wouldn't be MEE as I suspect he is 1st. rewinding the turn showed he had a trade treaty with me, then he didn't. I don't think it's worth redoing the turn as the few ships I had wouldn't have stood a chance and now I know what he is going to do.

[Captain Kwok]

I think your theory might be right. He probably broke the treaty and the message was lost by the "save and re-load" bug that we've seen before.