Yes. I believe sometimes my broker delayed my order execution and send a tip to a market makers. Market maker place a order better than current price and fill
For example.
With broker 1 (direct market acess) i send a order to buy 100 stocks for 10.0101
broker 2 always send orders to Edge ECN. I send a order to sell 100 stocks for 10.01
BUT order is delayed. mysteriously someone place a order to buy 100 stocks for 10.02
I believe my broker send a tip to market maker, market maker place a order better than current price and fill