I can only guess with what I have to work with so my best guess is he dropped the pedal on the ground and ruined something my first guess also being the pot. Another popular thing people do is swap chips and can easily mess things up past the diode protection. I have had that happen more than once and now I will always tack solder a chip in place so they can’t switch it. Also make sure the chip is properly seated as well. I would be using an Audio Probe along the entire audio path to see where your problem lies very quickly.