The 789 Potentiometer is cheap af, when I opened mine to check it was some knockoff Chinese brand trying to be Alps. I also had the same issue with the left channel being scratchy, and while the potentiometer IS desolderable, the damn volume knob is part of the pot, like it’s not one of those knobs you can get off the pot, it’s as if though the pot was soldered onto the board, and when the knob was put on, it was as if though it was designed to never be taken off, so you have to break the pot to get it out of the case or else the knob won’t let you remove the pot, and then you’d need a new knob too since again, the knob is part of the pot. Not bad if you keep the 789 since there are Vishay pots that can replace it on Mouser, but hurts resale value if you get bored of it and try to sell it on ebay.
Then again if you have a warranty, try sending it back, although they’ll still replace it with the same pot brand again.