Pathos Logos

I have a Pathos Logos integrated amp. It was working fine except last time the volume control has gone bizerk. As soon it comes on and the volume knob is increased to its first level the output goes crazy high. Tried it few time and it was doing the same. The unit did not have any problem prior to this. Talking to a service person in San Jose, appears to be EMI and or grounding issue. I cannot understand how one can have a grounding or EMI issue if no change to the system connection was made. Any comments will be appreciated, thanks.
Yaz