Luxury count delay

At the end/beginning of a turn when the AI offers a trade, i'll take everything of the table to make sure I have at least 2 of the luxury. I'll make the trade and then I have 0 of that resource!
I've now gotten in the habit of having my resource window open, but every now and then I still make this mistake. What gives? Why is the resource tally not accurate? This is definitely something recent, is this the result of a patch and what was the intent?
Thanks.

If I'm not mistaken, the problem arises when you have an old deal ending. For instance, if you have two Gems, but you traded one away, then on the turn this deal ends, the AI will recognize you have two Gems again and make trade offers on it (which is fine) - however once you accept a deal, the other AIs will still think you have two Gems available (which is the core of the problem) and also make offers on it, which potentially will have you trade your own copy of the resource away also.

This "feature" isn't recent at all, but has been in the game since the Vanilla CD release.

What did change during a BNW patch is that at one point the AI is much more frequent about asking about "renewing" a deal that had expired 20+ turns before.

I've been more cautious with resource trading, but still I wind up accidentally trading away my last copy.
Any advice for how to keep track of resources, and not trade them away??

If I had traded lux for lux, I'll accept a trade renewal offer. Otherwise, I refuse all trades involving my luxuries when it's not my turn. I'll figure out where I stand on MY turn and then offer the very trades I just refused once I'm sure everything's in order. The only time I consider deviating from this is if I know that the reason I'm being approached is because I had a worker just finish a duplicate and I forgot to manually finish it and sell it off myself. Especially if I have a DoF and they've got 240 gold for me.

Even if I think it's a proposed renewal, I'll usually refuse if it's between turns. I've taken to selling off luxuries prematurely to get money, gift CS, getting a unique luxury back, so I can sell off others and still stay happy. With all that borrowed happiness/luxuries, I can't afford to sell something off that I don't mean to.