problem sweet fx dub echo,channel number 2


hello, I have a problem with the mixer, on the channel number 2 the sweep potentiometer fx with the fx dub echo selecting, when I turn the potentiometer to the left and return to the center position it does not cut the fx sige sounding, I tried on the different channels of the mixer and does not have this problem only the channel number 2, is not the problem of hardware or firmware? my firmware is v1.1

video problem: