Check your nose wheel control linkage. If your linkage pushes for a right turn, and if your linkage is flexible, then the nose wheel will easily flex the linkage and turn left. I have had this happen when I didn't anchor one end of an outer nyrod or if the inner nyrod was too long (too much inner nyrod showing). Try moving your nose wheel and see if it easily moves to the left with the rudder centered. It will be solid trying to turn the nose wheel to the right since at that point it will be pulling against the servo.

This is just a guess based on my experience.