Hi Jerry,
The flatten feature did not submit a cancelation for the sell limit order. I manually canceled that order and tried to flatten again, and Medved trader did not submit a market order to close out. I have provided more detail below and screenshots from Medved trader and Webull.
Please correct me if I am wrong. I understand that the flatten feature should cancel any pending orders and submit a market order to close the position.
From 11:20:12 to 11:20:19, I attempted to flatten the order, which should cancel the sell limit and place a market order to close out. This did not happen. So, I manually canceled the sell limit order at 11:20:25. Webull accepted my manual cancelation. From 11:20:31 - 11:20:37, I tried again to flatten the order without success. So I manually submitted a sell market at 11:20:43 to close out.
Please note the screenshots from Medved Trader is PST and WeBull is EST time zones.