Yamaha yc45d low output

Hey all. I have a Yamaha yc45d that has very low output from the upper manual. I can hear all the features tied to the upper manual working but the sound output is very low. Also, it seems like if more than one key is being used at the same time on the upper manual it gets distorted. Lower manual works and sounds awesome! Everything looks clean underneath. No obvious loose or shorted wires that I can see. Any help would be appreciated