Jim, I took Brian‘s advice and also soldered the center post of my RCA socket vertically with great success. I experienced the same problem with excess flux running down the center post that caused movement. I reworked my solder connection with new sockets vertically as Brian suggested and I am very pleased with my new results!
BTW: I am an hour give or take from entering the testing phase and trying out my first track on the preamp…… I’m so excited!