I would think that it is the set up of your Rip program more than the printer. The program still thinks it has 3 white channels therefore when you do a light shirt and select that enviroment it swithces of the 3 white channels or in your case the LM,LC and G. I would go into your colour channels and see what they are set at. I think that you 3 lights are still set for the white underbase. You will have to change all the settings to get them to run properly.