Greetings! Lately I have been buying AP resets and sometimes the trades end with a message saying "Trade unsuccessful". The person does not have max mesos, and I have more than enough space. The AP resets are split into all 9 slots, 1 in each. It seems to be random when it happens, and after a few tries it just works again. I have tried to find the cause of this but it just seems to happen randomly. You do not have to relog to fix this, but I have found that relogging often helps.
Today I traded myself about 90 AP resets, it wasn't working at all until I started alternating between who initiated the trade request between both of my characters. Suddenly the trades kept ending successfully.
I just tried again just now and it didn't work, and then it did, and then it didn't. It is just very bizarre.
I've had thus problem too and how i fix it after i get the "unsuccesfull" trade is; trade something else first (like a etc.), then trade 1 AP reset and after that you can trade 9 at a time again.