Wojtek, I feel your pain.
I have a system-5-M.
Hate contacting AVID,
getting contact through their main website and or the main USA phone number +1 650-237-1604
is not fun.
first off, what is wrong with your fader. If the motorized portion of the fader does not work, the audio portion does. In other words if you wrote automation using a fader that does not have a working motor, the system will still track the the automation moves. I have had a few motors go out and have had to buy the whole fader pack. If you can love without the moving, you can still work just fine.
If the fader sticks, or chatters, then the fader mechanism needs to be cleaned. There are actually 2 contact strips inside the fader, one for audio, one for the touch sensitivity. if the fader chatters you need to clean the touch sensitive part which is under the top glide rod. I usually hammer a Q-tip flat and then using isopropyl alcohol clean the resistive strip. If the fader sticks then you need to clean any gunk off the glide rods, and then lubricate with a very fine fader oil. I have also found broken wires to the fader, either at the fader end or at the header connector going to the fader control board. I am not familiar with the physical construction of the MC-Pro, but on the system 5, the faders can be accessed by a removable pannel underneath the unit. (turn off power before disconnecting anything !!!)
If you can buy a replacement fader, and access to the faders is a easy as the S5, all you have to do is open the panel, remove the fader cap, remove the 2 screw from the top and bottom of the fader, and disconnect the faders wires at the PC board header connector. be careful these wires are sensitive, I have had to re-solder a few wires back to the header connector. also be careful when pulling the fader out that you do not snag any of the wires for the other faders.
Really with common sense and care replacing a fader should be easy.
I tried to find a picture of the MC-pro on AVID's site and could not. Have they been discontinued ???
PM me with contact info and where you are located and the exact model of your unit and I will see if I can find a contact for you. Also see if you get better results with that phone number I posted above.