I was in a trade with someone and I had put 14 jps in (made sure they were on my side) and waited for them to enter the money. Right as they put the money in and accepted they logged off and got what was in my side as well as their own side. I didn't accept the trade at all yet they got everything.
please make a bug report about this and if you don't have a recording of this trade i'm afraid staff can't help you.