My rotary cutter blade became really loose (wobbly) and I had no control over the blade.
The blade was hitting the ruler at various locations along the straight edge, DH looked at it, and then put in a small washer on the same side as the screw, spring and plastic - not on the blade side, that tightened up the blade and no more problems with the cutter or blade being wobbly.
My blade was nicked from hitting the straight edge of the ruler. I purchase all my Olfa blades from LP Sharp, and
have found no problems with these blades. I also send them my used blades, I just don't like to put dispose of them myself.