I had something like that too, with an early generation DC END headset. I never really did get it working the way I thought it should. I took it to the avionics shop, and they said it was working properly. It hangs on my wall to this day. I did buy a later model DC OneX headset, and it was vastly improved, I really liked that one! Unfortunately it's at the bottom of a lake now
For the ENC headset you have, try moving it around on your head, and switching sides on it, that may help.