I think it's a display problem on the IB platform. If all of the legs on the combo did close at -0.20 price and your P&L corresponds to it, it should show $-0.20 not $-0.10. That $-0.10 is just the wrong price displayed. You have to realize IB is constantly doing "updates" to their platform and f***up happens all the time. The developers that they hire are not the best. It took them so long to just fix some simple bugs in the "Strategy Builder".
Respectfully, this is not some sort of display issue. Remember that I placed the order as LIMIT at -$0.10. So filling at -$0.20 is where the failure is. It should never have filled at that price. If I am saying I don't want to pay more than ten cents, why did it fill at twenty cents?
That is weird. If your limit price is $-0.10, it shouldn't be filled at lower than $-0.10. You are right. What do you see on the audit trail on your side? You can call it up on IB to see. Does it say that your final price when you entered the order as $-0.10? Did you change the price to $-0.20 at any given time before you changed it to $-0.10? It could be that IB never received the final $-0.10 that you entered and already filled the order at $-0.20 before you changed the price to $-0.10. With all the system issues that IB's having lately, I won't be surprised if that was what happened.
I did not change the price. IB support confirmed the order was entered at -$0.10. IB support checked the audit trail and confirmed the order filled at -$0.20. IB support has escalated the matter. I am growing old waiting for a response. I see now that this is not an isolated instance.
You are going to have to follow up and ask to speak with a manager. If this is not a system issue then this is a fair dealing issue. Good luck!