24v relay switch is always on and only getting 16v.

I have an amp where one 24v relay switch (speaker B) is always powered (only suppose to be on when B channel is select) but only 16v it's getting and never changes.

Turning it to A+B, A, B switch lower all 5.1 + B channel volumes down a notch.

Turning the switch off turns off all channels but B channel and B volume goes louder.

All 4 relay 24v switches were replaced.

Relay 1 for 'front A left and right'

Relay 2 for 'center'

Relay 3 for 'rear left and right'

Relay 4 for 'front B left and right'. 16v is only what it's receiving and never switches off when I turn it off.