mine dosen't move at all. sounds like the part o the visor that you insert rod into has enlarged - if so just put a rag in hole and ram rod thru. i need to stop my mirror from dropping and thought of putting some steel wool into socket/ball interface,
If its at the mounting point to the header they have a spring and clip on the back side to provide pressure on the rod to keep it from moving. Take off the mount, compress the spring and add a washer or shim or two to compress the spring to restore the pressure.
If its the visor moving on the rod there's a compression clip inside, kind of a question mark shape. You can clamp on the visor to close the bend up with the rods out, or shim with some real thin strips of metal (very thin). Alternately you can try to pull them out and recrimp them, but they ae a bear to get out and you can damage the visor.
You could also rechrome the pins to increase their OD, or drop $30-40 and just buy new ones.