Cancel/replace an executed trade

It appears that I can sometimes cancel or replace a trade which should have already executed. I’m trading @NQZ4. I will admit it does give a system vendor the ability to ‘improve’ their results, but its not good for their customers.

Anybody else seen this?

Can you give me an example of how you accomplish this. (i.e. was this a stop/limit that you think should have been filled in the time before entering order and canceling)? In theory the system checks for pending fills before allowing a cancel, but it is theoretically possible that it misses some (in the interest of speed it works with 60-second granularity - meaning it might miss if the fill would have happened within 60 secs pre- cancel). Thus I’m interested in knowing how easy it is to replicate this and in what circumstances.


Thanks to Trader DTG for pointing this out. Problem has now been fixed. Unless you are Superman and can circle the Earth fast enough to cause the clocks on the planet to move backwards, you will not be able to XRplc a trade that ought to have already taken place.