] Hi. That was the easiest revive with the most significant result I've had. I just cleaned with 70% (no perfume) alcohol, soft toothbrush, thoroughly clean the boards, used a swiss knife's magnifying lens to really check up close if it's perfectly clean.
It seems to be the soldering paste used in manufacturing which gets in contact with what shouldn't be in contact and probably somehow the paste ground the board, messing with the potentiometer, so that, although the it moves, it's a delayed reaction. Thank you. God bless. Rev. 21:4