Glenn Irwin finished sixth in Sunday's British Supersport feature race at Snetterton in England.
Irwin remains third in the standings but fellow Carrickfergus rider Alastair Seeley slips two places to fourth after crashing on the warm-up lap.
Graeme Gowland won to complete a weekend double with series leader Billy McConnell second and Luke Mossey third.
Jordanstown rider Andy Reid came in second in the National Superstock 600 race and leads the series by 22 points.
Seeley was well placed going into the feature race after finishing second in Saturday's sprint race.
However, he now trails Englishman McConnell by 31 points and lies three behind Irwin.