I had my first ever trade problem yesterday. At the end of the day, I shut down TWS and noticed a short position that was not there before. I dug into it and found that 100 shares of a 200 share trade from early in the morning had been canceled. The cancel time was 16:40, after the close of market. I had exited the trade hours earlier, so now rather than flat, I show a 100 share short position! It changed a winning trade into a loss. I got on IB chat at about 5:00pm and the rep told me that there was a problem at the exchange, EDGA, and the exchange sent them a email that they would cancel a bunch of trades and restore them "shortly" The rep told me not to worry, I am flat. But, today, my account still shows a short position and no one answers IB chat or responds to tickets. If I am getting stuck with the unexpected short, then I need to close it ASAP. But if I am really flat, then if I buy it in, I will be long. I have no idea what my true position is. This is scary. I do automated trades. If a closed trades start getting unwound after the end of day, it would be a real mess. Plus, I doubt a loosing trade would ever be canceled. Is this normal? In three years of trading, I have only had one other busted trade before, with a different broker. In that case, I got a phone call within 20 minutes and it was removed before the normal exit. This is a mess.