no update about the order book bug yet?
We think we've fixed all the issues people were seeing, and all those fixes are now live. So please let us know if you see anything that still doesn't look right.
There were a variety of cases, but all of them were caused by a bid > ask condition. For example, suppose the book contains these orders:
sell 1 lot @ 130
buy 0.5 lot @ 127
buy 0.5 lot @ 120
sell 0.5 lot @ trailing stop 126, limit 100
buy 1 lot @ 110
So current ask is 130 and bid is 127.
A new order is placed to
buy sell 1 lot at 125. The order picks up the 0.5 lots @ 127 and then the rest of it goes on the book as 0.5 lot @ 125. Now the current ask is 125 and bid is 120.
The 120 bid triggers the trailing stop @ 126 and puts in a limit sell order at 100. Now the bid is 120 and ask is 100 (bid > ask condition). If the ask side initiates the trade, the trade will be done at $120. If the bid side initiates the trade, the trade will be done at $100 (which appears to have skipped over the buy @ 110).
So those of you who thought you were being skipped over, you weren't. It's just that someone with a higher bid in the book got filled at a price below your offer. Of course, the converse could happen too, where someone on the ask side might appear to have been skipped over when in fact someone with a lower ask just got filled at a higher price.
In one sense, this isn't really a bug, because whichever side initiates is supposed to get the best offer on the book from their perspective. So if the buy side initiates, they should get the lowest ask on the book - i.e. $100 in the case above. It's just that when bid > ask, this normally sound principle leads to unexpected price action that doesn't look right. And we'd probably be answering support tickets and questions on social media forever if it wasn't fixed. In the scenario above, the fix is that the trade will execute at $120 regardless of which side initiates the trade. That seemed the best solution, and will avoid the strange price action, but it also means that the side initiating the trade under this bid > ask condition isn't always going to get the best offer on the book (as they normally would when ask > bid).