Sorry once again for the late reply 😞
I can't replicat this for whatever reason.
I also use the Rudder Axis to steer the aircraft and it turns in circles no problem. For testing I also assigned a button to the tailwheel lock and that works as expected for me as well; when activated, the plane no longer turns - or only very little - but as soon as I release it again, the plane starts turning.
Are you positive, that there is no other control binding interfering with the controls of the plane?