Noise over Audio during use

[admin]

I am not sure what to tell you.  Nobody else has reported any joystick issue, and I have never seen this problem on any of my systems.  Bad 5v power can cause things like this though.  Measure 5v and see what yours shows.  Low 5v will cause the screen flicker (the VIC is very sensitive to voltage).   You could also try swapping the 6526 VIA chips in your C64 and see of the problem changes or goes away.  The VIAs are connected to the joystick port and user port.