Ok hang in there
How are you coming into the mixer from the u-control outputs?
How are you coming into the mixer from your microkorg?
What model is the mixer?
What output are you using getting back from the mixer to the input of the u-control?
Where exactly is your loudspeakers or headphones, if that's what you use, connected?
Did you choose the u-control to be the (only) audio device in Reaper preferences?
Can you make a screen dump (cmd+shift+3) of the Reaper mixer and snap a picture of the hardware mixer setup (showing the knob settings).
Then..
we should be able to solve this.