Now also getting another error message from Oanda:

"market_order_reject","rejectreason":"units_precision_exceeded","instrument":"eur_nok","timeinforce":"fok","positionfill":"reduce_only","reason":"trade_close","tradeclose":{"units":"5045.900000","tradeid":"464"}},"relatedtransactionids":["623"],"lasttransactionid":"623","errormessage":"the units specified contain more precision than is allowed for the order's instrument","errorcode":"units_precision_exceeded"}
Error 075 [EUR/NOK:Trend:S00464] - close attempt 2, 50459@10.27 at 10:00:02

Decimal places not permitted for currency orders. Decimals only permitted for Index CFD because of the change earlier this year to lower minimums.