My toughest loss was in Jan 2004 trading ZB 30-yr bond futures. Had a 10-lot short going into some employment report with position up +'8 ticks in my favor. Stop was at -'8 ticks from entry, which gave a full '16 ticks cushion from current market to stop order.
The news came out, bond prices flew upwards in my face for a bit more than two full points and obviously that trade was toast. There I sat, waiting for the fill report to come back, but no reflection. I waited two minutes (seemed like two hours) and called the broker. They called the floor, and it turned out my short position was still live.
Seems that the CBOT stopped accepting stop orders inside, so orders were held in the software bridge from clearing house. At that moment in time, new CBOT electronic routing still had some glitches that were discovered during high volume surges. I was told there were four main trunks of traffic routed into the CBOT at that time, two were operable and two were frozen. Guess which ones my orders were trapped inside?
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By that time the ZB had relaxed off its highs, the broker closed me on a verbal order for -'40 ticks from entry. That was not my biggest one-day loss, but it was the sharpest pain because I did nothing wrong technically.
Lessons learned? Don't trade bond futures ahead of big econ reports... that is best left for FX markets with the right broker/dealer. (fwiw... GFT has always filled my FX strangle orders into econ news without any games)
I have never since traded any contracts on the CBOT, and don't intend to. Call it a personal thing, but the CME is where I remain. Have traded thru two CME outages with live trades working then, offset by broker calls to the pit with big SP00S contracts to hedge.
Moral of the story? Keep those risk levels tolerable. If something global shocks the market later today or any time hence, eminis could go lock-limit in a flash.