Mux Shield

I managed to get readings in the midi monitor by pushing the back side (the side where the analog pins and the low digital ones are) of the shield further into the arduino then seems reasonalby necessary. I'm confused, because earlier - when the midi monitor showed nothing - the power led of the shield was on, so I assumed the shield was placed properly. Also, I assumed that the shield ought to be placed horizontally on the arduino. Now it's back end is significantly lower than the front side..

Although I'm happy that the midimonitor receives midi, it's still not the data I want. There seems to be something wrong with how the data are send. I think the control look up table doesn't function properly. When I want to send data from 1 potmeter with 1 Midi CC value, I receive changes of multiple Midi CCs. I attached a screenshot.

Could this have something to do with the placing of the mux shield or is it something else (like the control look up table)?
Btw, when the shield is placed not horizontally, the programm the sends midi notes works properly.