Ben Wilson's British Supersport title hopes suffered a blow with two non-finishes at Silverstone, while arch-rival Alistair Seeley won both races.
The Gearlink Kawasaki rider from Boston crashed out of race one after a last-lap clash with Seeley.
Mechanical problems forced him out of race two as Seeley opened up a 14-point lead with one round of the series left.
"The championship is far from over. I will keep on fighting right to the end and see what unfolds," said Wilson.
"I was on course to win in the first race and thought I had the line.
"Seeley thought otherwise and moved back on me and we clashed, but it was deemed to be a racing incident.
"Going into the second race I was determined to claw back some of the 25 points lost and I was beginning to reel him in and perhaps could have caught him in the last few laps but lady luck wasn't on my side."
With the title to be decided in the final round at Brands Hatch, Wilson, who had a 36-point advantage prior to Silverstone, admits: "We have to put this weekend behind us and concentrate on the final round where we have three races to contest.
"It is still mathematically possible for me to regain my position."
In British Superbikes, Lincoln's Alex Lowes was seventh in race one for Motorpoint Yamaha but crashed out of race two.
Louth's Peter Hickman crashed spectacularly in race one but was unhurt, going on to take seventh for Tyco Honda in race two.
Lincoln's Lee Jackson was 26th and 23rd for Buildbase BMW while Shane Byrne and Ryuichi Kiyonari of Louth's HM Plant Honda team saw their title hopes all but disappear, Byrne taking a brace of fifth places and defending champion Kiyonari picking up just three points for 13th place in race two.
Race victories went to the series leader, Crescent Suzuki's John Hopkins, and TAS Suzuki's Josh Brookes.