Window Winder Woes

Old Fogey UK
Old Fogey UK Expert Adviser
My car is a 1934 LTS that doesn't have vent panes, just solid wind-up windows.
I've developed a problem with the driver's door window.
When I wind it up, the top of the glass goes right up at the back but droops at the front, leaving a gap of 1/2 an inch or so.
I've taken the door panel off to have a look inside and can't see anything that might have come adrift.
I can get the front of the glass to locate properly by shoving up the front end of the glass retaining channel and it stays there, but as soon as I operate the mechanism it drops again.
Is there any way of adjusting the winder mechanism to stop this happening ?
Or, as I fear, is the mechanism simply worn out because of 88 years of use ?  :'(