It could be just me...but I've had a great number of instances the past few months when setting market stop limits on equities at IB, to have them quickly hit then bounce back. Both short and long trades. Recently, I've moved to setting stops via my software platform with auto-entry, and haven't experienced the same problem. Maybe it is my imagination. But maybe not. IB tells me of course that market stops are not sent to the market, which is why I use them. And I don't know the details of IB's internal setup, but I'm wondering if IB has an internal trading operation that could be reading stops set in client accounts. Anyone else have similar experiences, or further knowledge?