Hi Stupot,
as you have got not more than 48 faders, you have to program your additional dimmers as "fixtures". You can control them by using the MFKs and the right wheel (choose "position").
To patch the additional dimmer to DMx-adress 49, you push the first MFK on page 1, if you are to choose a destination. After that, you can press MFK 1 again, hold it and press MFK 20, you patch automatically 20 new dimmers to the MFKs on page 1.
Because of malfunction of output: maybe you have to raise the Grandmaster and Preset-A-Master?
Hope it helps
Jorge