Weird Motu 828??? What's Causing This?? Options

[-spike-]

I am having a problem with my motu 828 my level volume and main volume knobs doesn't seem to control the volume of my monitor output (outs 1-2) what ever I do, turn it way up or way down they have absolutely no effect on monitors output (outs 1-2) but when I plug a headphone in the headphone jack the level volume and main volume knob are controling the volume of my headphones but not the monitor outs.

I have read an article in the motu website on how to configure the level volume and main volume knobs to control only the heaphone or monitor outputs by opening the motu 828 and simply switching a wire, I have searched for this article again and I couldn't find it anymore.

I bought my motu 828 second hand and it is very likely that the previous owner has done this modification to the motu 828 anyone out there know how to undo this??

or is my guess of the source of the problem entirely wrong? if so what causing it?