Having problems shifting the vehicle into first gear from a standing start

My problems started with a leaky slave cylinder, which I had repaired, since it was an internal slave the mechanic suggested doing the clutch as well. After the repairs, I'm having problems shifting the vehicle into first gear from a standing start. The mechanic tried to bleed the slave again it did not help. I noticed the clutch fluid was very dirty as well. I took it to another shop that had a pressure bleeder and they sucked all the fluid out and fully bled the system. This did not help. The mechanic suggested replacing the master cylinder which I did have done by another shop and the problem still exists. It does seem to get worse, when the car gets warm, after about a half hour. One mechanic suggested that they might have over ground the flywheel when they did the clutch and the slave cannot push the clutch out far enough. To find this out it would mean dropping the transmission again. Any ideas? Any help you could offer would be much appreciated.