I have never had this issue before, however, i am getting this rapid clicking noise when i use the distortion loop. I have had the unit for 2 years and never a problem.
1) it happens whether i use the upper or lower loop (only in distortion loop mode).
2) its not the pedal, have checked several
3) Not the cables, used different ones.
4) Not the power supply as i tried a 9vlt battery.
I am running the latest beta version 3.2.73 - this is the only thing i can think of that is causing the issue.