Firstrade also has a $1 million 'firm limit'. Which means that any position established for more than $1 million in credit will not be accepted.
The COB is monitored by market makers looking for an edge to their values. If they send your order to a broker, no MM can see it unless they show it. The broker will try and work the order, but small orders can be ignored. I have no idea if they are doing this.
When I was with Tastytrade I had the same trouble getting orders to fill, especially at the mid price. Both Firstrade and Tastytrade clear through Apex. I'm seeing a pattern here.
My point was it not a broker issue. You would have the same fills in the SPX with another broker for the reasons I mentioned. If you assume midpoint is fair value, you shouldn't assume you should be filled there. This means there is no edge for the MM.
Yes I accept that point. But sometimes there is nothing wrong with trading at the bid/ask. These fluctuate a lot as well with my strategy. But mid price is a cheaper way of trading, not to mention I was able to fill at mid on entry a few times. Firstrade has never filled me at mid on exit, in fact I have been unable to exit my trades at all with them so far. And I have lost money as a result of this.
You are overly suspicious. Simultaneous orders don't get filled because there is no one on the other side. It is the While West. Option Market makers can do whatever they want. Plus there are latency issues for the retail trader. The more complicated the order is the less likely there will be a fill.
Interesting. What do you consider the latency that is acceptable on a retail trading account located in the USA?