AR MKI volume Low output 7/8 only

Hi , just bought used AR , it have low output volume on MT and HT pad only…

If I turn some knobs on overbridge sometime that “unlock” the volume and it work fine again… but if I turn of the machine , and turn on volume is low again… All others sounds are OK … just the Mid TOM and Hight Tom, with synth or sample it’s the same…

Have you checked the voice routing page to see if they are going through the main and fx outputs?

strangely when I move overdrive knob on the AR , that “unlock” MT/HT volume… I don’t understand if this is a hardware problem or just a bug…