Gerber Sabre 408 Y-Axis Leadscrew Issues

Hello all, we have a Gerber Sabre 408 cnc router. We've had an ongoing problem when routing circles or anything with a radius on the Y-axis. There is always a flat spot at the top of the circle, particularly right where the Y direction changes. The leadscrew is worn out and will need to be replaced eventually, but management doesn't want to do it right now. I am pretty certain the problem with the flat spots is due to wear in the anti-backlash nut. The nut on this machine uses a spring to keep the 2 parts of the nut together, but I believe the threads in the nut and/or the spring are worn out and not properly tensioning the nut. I noticed that when I turn the spring in the opposite direction to keep the 2 parts of the nut spread apart, I was able to rout perfect circles. However, when I tried to rout a bunch of letters out of 6mm sintra, the flat spots returned on the letters that have a radius. I believe this is because the router is moving in different directions more rapidly than if I were routing just circles, and the spring is giving out when there is an abrupt direction change.
I am thinking of modifying the leadscrew nut to somehow keep the 2 parts pushed away from each other. I do believe this would increase the wear on the nut, but this is just a temporary fix until we replace the screw and nut. Does anyone have any ideas as to how I can do this without removing the nut from the leadscrew? I can work under the machine and I have clear access to the nut. Im thinking of putting some type of spacer between the 2 halves. Will this solution work to eliminate the backlash when routing? any suggestions or advice would be appreciated. I am still a fairly new operator. Thanks!