Let's say I short a stock and hold it overnight. And let's say it's doing very badly and the stock is gapping up over 100% during after market hours. Since I can't use a stop loss during extended hours, my loss keeps accumulating until the market opens.
My question is, could my broker issue a margin call and liquidate my position before the market opens? Otherwise, by the time the market opens, I'd have lost over 100%?
Also, have there been any cases where the loss keeps accumulating to the point where you actually owe the broker money?