In June 2011, I had the clutch pedal drop to the floor. I took the car to United Auto Repair on East 83rd St., NYC, and they replaced the master and slave (close to $500 p&l). I had to take it back immediately after for them to bleed the system correctly since I was getting a grind going into reverse. January of this year, the pedal went soft and I took it back to them. They replaced the master cylinder pro bono. A few months later, I'm again getting a grind going into reverse and nasty shifting in general. Pumping the clutch pedal a few times generally gets rid of the problem for a while. I've had it back to them to re-bleed the system and adjust free play -- to no avail.

I'm not visibly losing any clutch fluid, so I don't think it's a leak unless it's very small. What should be the next step in troubleshooting this irritating thing?

I feel like I've given them ample opportunity to fix this correctly, and I'm ready to try something else.