I don't have an Olfa rotary cutter, so don't know if this applies to your situation.
One of my rotary cutters came with a washer. When I changed the blade in it, I apparently dropped the washer while removing the blade. In other words, I never saw the washer. When I finished putting the new blade in, I had an awful time cutting!
I finally threw the darn rotary cutter out, and bought a new one. When I changed the blade in that one, I saw the washer, and the proverbial 'light went on' about why the other cutter didn't work well.
One last thought...do you have any knicks in the ruler? If you do, the blade could be going into one of them and be knicked by the impact.
Last edited by cathyvv; 12-07-2013 at 02:08 PM.