This is probably one of those things where you have something that is wrong or that was done wrong where if it was in any of our hands we'd just see it straight away and be able to tell you what to fix. But when you're dealing over the 'net it's impossible to do more than accept what you're told.

Just for the heck of it use the RC system to deflect the rudder over and then try to lightly push it back with a finger. Wood or not sometimes odd things can happen that result in pushrods bowing under load. You won't need much. THe air forces on a rudder that size are not more than a few ounces.

Um... what size diameter of prop is on the motor? I ask this because I had a model that used a prop that was a sizable % of the wingspan and the model was, as I recall, reluctant as heck to turn to the left but would almost snap roll to the right with a hint of control. A friend noticed the same thing but not quite to such a strong degree with another model that had a fairly large prop for the size of model. To confirm this you'll want to test glide with power off out over the slope of a gentle hill so the glide is extended enough to test the rudder response in both directions before landing. If this test glide is successful at least you'll know it's motor and prop related. From there you can add some thrust line compensation secure that you're not hiding some other issue. Of if the thrust line adjustments still leave you with some funky handling issues go the safe route and swap out the motor for one that will work well with a little smaller propellor.