Help troubleshooting Cavalli Liquid Carbon

Hi,

just bought a pre-owned Cavalli Liquid Carbon (V1 not massdrop) from Head-fi
The first day is fine, but in the second day when I turned it on I found my LC have some problems with the volume;
btw I used 6.3 jack my XLR is on the way shipping,
the sound from left channel is super large, like turn the volume to 10-12 o'clock and I can not adjust it
After couple mins, the sound from left channel became lower, but still around 9 o'clock and when I turn the volume all the way down to minimum I still can hear some sound from the left channel.

Anyone has this problem before and have advice how to fix it? I havent try XLR yet I dont know is the knob problem or jack problem

Thank you
Ryan