If it isn't the power supply check the Ribbon cables inside. Use hot glue gun to glue them back so they don't come loose over time.
Power supplies for some reason are a real bad design. What ever they use for the outer casing is crap. Hate to say it but my unit has very little gig time and it stays in the house and goes now and then to another room but I noticed that the end that comes out to the pedal side, right at the pack on the relief it breaks the casing exposing the wires. I have tried to remedy this with some liquid rubber just to keep it from exposing and shorting.
Line 6 Pay attention, because customers should NOT have to buy new power supply units for defective design flaws. You should allow the customers to trade them in should the company redesign them. It isn't just this company but many headphone cables are the same way. The oils from your hands and day to day use they just crack and break apart under no abusive usage.