I get filled as the price moves up or down to the next price. For instance, my order is placed at 25.50. By the time I get filled, the price is already trading at 25.75. From my experience, I would say that is the case about 80-90% of the time.Are you sure it just doesn't look like you are filled last, while in reality all the traders behind you in the queue just cancel the moment the price reaches your level instead of getting filled? (that's for true fifo markets, in equities or options for example different markets vie for the first fill in parallel.)
I also use OEC and AMP. They all have the same problem.