This!!!
It looks like there is a new steel top spring in the pic, but you said you've replaced? Just making sure... In the pic the geometry looks backwards. Not only is the unit too close to the rudder, but this is also the main cause of tail wheel shimmy. The "vertical" post that swivels and comes out of the top of the fork should actually lean with the top to the rear of the plane and bottom closer to the front. Need much more angle.
I agree about straightening as being probably sufficient rather than replacing.