Sometime ago I read a post where a user of OpenLedger complained about the trade engine not matching the trades properly. In specific, higher "Ask" trades were executed before his lower ones, if I remember well.
I did check out his claims and they are true. Though, I would like to point out that it might be a bug, or that someone is trying to inflate the price of an asset by selectively trading between or among different accounts.
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From @skriptroid