Cret,

Can you outline what was involved in fitting the DRO... or what was taken apart to fit it? I dont know the C3 but I have a similar movement in my ancient lathes and this is simply wear on the nut. What I did find was stripping them down and rebuilding them had a big effect until I discovered that the nut wears differentially and was reversible... accidentally refitting it back to front increased the backlash by 2mm!