r3 audio problem - hardware troubles :/

[stopi]

Sometimes in my R3 only one of l/r channel sends audio signal. During it also vocoder doesn't work properly - no sound on XLR input. Sometimes vocoder sound appears when I set gain knob on max position. I experienced that mod-wheel is detunig sound almost 1 semitone up (!) independently of preset change. What can be problem?? It looks as connection/soldering problems on internal boards or ant voltages interferences between mod and pitch wheels. Just made in China :/