Have you found any slop in your pedal assembly?
Is the slave push-rod properly seated in the release fork?
Is your master cylinder linkage adjusted properly?
If your master cylinder linkage is adjusted out too much, the feed port from the fluid reservoir will never open to the master cylinder, so the slave will never "self-adjust" like it's supposed to because it only has a fixed volume of fluid available. (e.g. it will stay mis-adjusted)
just a hunch -something to check