"Backing Away" is illegal. But I will 'splain. Trader published a quote and got caught, so did not "back away", you got a partial fill. Trader set up if got filled he/she would move to a certain px. And after that does not owe you anything.
This sounds like you are going through Etrade, worst executions of all time. I would suggest moving to TDA or Fidelity for trading. I never worked for Fidelity, but they have, in my professional exp. Fidelity was the, well NFCS clearing and gave and will give you the best executions.
I can promise you, it was all manually set up in the system, no High Frequency Trading on pinks.