Sir Terryb . . . . .
I feel that your situation is 43 years of time and possible tension decrease of 2 coil springs, plus a dial cord polishing plus 3 1/4 turns of coils of loops of the dial cord around a 1/4 inch tuning knob shaft.
With the day one condition of that tuning shaft being a MATTE surface, but in the interim use time, it has transitioned its peripheral surface to a glass slick and smoothly POLISHED shaft.
The easiest fix now, without a teardown, would be the luck of you having some liquid rosin flux as is used for electrical / electronics soldering.
The next best hope if you do not have such flux is to get a rosin ball droplet from a donor pine tree, and dissolve with denatured alcohol.
( OR do you, or an acquaintance play the fiddle ? . . . . .a . . . la . . . rosin for its bow. )
Place on a Q-tip and apply to the 3 1/4 turns and wait until the knob starts gripping and can move the dial enough to get another fresh 3 turns of dial cord dampened . . . . . repeat until end of dial cord travel is reached.
Then you back track and cover the treatment of any earlier dial cord, that did not get treated.
Move the dial every 5 min or so until its rosin treatment dries, so that no lock down could occur.
If you ever want to peel the WHOLE banana, here is its dial cord stringing info.
Re . . .
I listen to in my workroom
Now if that workroom involves woodworking and airborne "micro" sawdust . . I can see recurring problems.
HOWTODOITTOIT . . . .
73's de Edd
.....