Probably a computer algorithm that detected a large price change in the security and sent in the orders automatically.
If you failed to file before the time deadline, this is normal behavior by exchanges. They will ask the counter-party to willingly bust the trade and the counter-party always says no. Would you give up a $40k+ trade for someone else?
Does anybody knows what will happen if I win? Will I get the shares back? What if the buyer already sold thoses shares? Will I receive the money that I should have got from that trade?
Again no justification for a bust here if there was an 8.85 limit with a 6.40 bid. Plus the story keeps changing. If the brokers log shows they received an 8.85 limit - which is one hell of a coincidence when the limit was alleged to be 18.85 then they actually delivered a good fill and there is no reason to ask MM/Dealer to bust. it would have been voluntary on their part. We can debate this, but without a trade log it looks good. After hours with earnings due pre open the next morning. I'm kind of surprised the after hours market wasn't 100 up and monster width. If it was an 18.85 limit there should have been no fill. 8.85 limit the fill should stand and there is no basis for a bust. Get the trade logs. A reputable broker will give you the trade log session.
$8.85 is very far from the precedent trade of $18.876. Also, between $6.40 and $8.85 there is a a difference of 20% as requested by the 7.10 rule of ARCA.
That is an irrelevant fact. Price action the next day is also irrelevant. Ask anybody on the forum how they would have bid it after hours with earnings pre open the next morning. We all would have defaulted to the max allowable width and the smallest allowable size.
But still, if the rule is 20% from the reference price it should be the only thing that matters. After the earnings release, I would inderstand that someone cannot asked a trade to be cancelled if he sells volontarily at a much lower price than the closing price of the day before. But in this case, there was no panic selling. It was only the second trade after hours at 4.21 pm. Clearly, there was no reason to do such a trade. I feel that it is clearly an erroneous trade.
ETH with a visible bid below yours. You might also want to consider asking the moderator to take down this entire thread so it's not used against you. ARCA was made aware - you state that. They saw no violation and they reached out for a bust that would have been voluntary - again they did their job. You filled well above the best quote. All that is going to matter here is the trade log.