This was a problem between the understanding of the system and partly due the system lags.

I queued to sell off my shares. When the market open, the price gapped down and hit my queued price. However, it did not reflect immediately which I didn't know about it and the system are actually in the process of executing the trade. So I went to cancel the queue and sell of manually without making sure that whether the order has successfully cancelled. In the end, this was a double entry which means I already sold off my shares through the queued order and I SHORTED the counter. I called my brokage firm to clarify, however they ask me to close my position as soon as possible because it was not the system fault. After a 5mins talk with them, guess what? the market rebounded. I have no choice but to close the positions. This was a LOL mistake I have made. Lessons learnt, make sure when you cancel your order, wait until it to prompt "Order Successfully Cancelled"


SHORTED by mistake