Did you resolve your issue
I have the same message when I m trying to close a forex option
{
"dealId": "DIAAAAPEEEMF3AJ",
"epic": null,
"expiry": null,
"direction": "SELL",
"size": "1",
"level": null,
"orderType": "MARKET",
"timeInForce": "EXECUTE_AND_ELIMINATE",
"quoteId": null
}