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I built my own application where I manage all of my open orders on my application because IB routinely missed stops in my markets (futures.) It wasn't an occasional deal- if there was market-moving info, the stop would be blown thru. Mind you, these are the stops IB maintains- if you place a LMT order on the floor the order won't be blown thru, of course. But IB will also fail to execute a hidden LMT.

I was disgusted by this, but then when I went thru every line of the CPP API I found the culprit. IBs logic is to execute a stop if the current relevant price is less than one tick away from the target-Limit. Yes, you read that right- IB does not use inequality logic (properly, they would Buy if the Price is Below your LMT), rather an Equality logic (they Buy if the Price is Equal to your LMT). This is amazing hackdom by IB, probably costing their algo and HFT traders millions of dollars each year. They are worthless for stops/limits, and you need to have a plan for thiis if you engage in HFT.