I got a call today from a friend who said the hum shields on a friend’s APR-5003 were not working.
I recalled this had happened to one of my machines in the past.
Removing the cover surrounding the heads will expose the mechanism—of course the heads and pinch roller need to come off first.
Cleaning and lubricating the rods and other parts of the linkage should make all well again.
I used Zoom Spout Turbine Oil.