A quick scan of that velobase site:
Altenberger
BSA
Campagnolo (Rally,Gran Sport, GT, Sport)
DNP (various)
Favorit (PWB)
F&S Torpedo
Gambato (Allvit clone but I needed a G)
Huret (Alvit,Challenger, Duopar, Eco,Success)
Importadora de Bicicletas e Acessorios
JIC
Kharkov (Type 1)
Lewis
M

There's no M.

Oh well.

Ironically it is not the high precision, nor necessarily the (control of) manufacture by Campagnolo that is the fault.

The D-ring or other fixing screw will loosen if there is sufficient clearance between the flats on the mounting bosses and the friction washers of the shifter.
In that circumstance the washers and screw will rock back and forth as the shift lever is operated, and gradual loosening is the result.
So yes, some auxilliary methiod of keeping it from moving is required.
In the past I have resorted to taking a punch to part #174 so it is a tighter fit.

This is a design flaw - the better solution to keeping the friction assembly immobile is that used by Simplex et al: an external tab that fits in a slot, the sides of which can be easily squeezed to take up all the clearance.

.

I seem to remember that there was enough slop in the system to allow moderately high cable tension without nudging the derailleur inward or keeping the chain from settling down onto the small sprocket. The pre-indexing sprocket spacing was pretty wide, after all.

Funnily enough, many racers deliberately left the front derailleur cable loose enough so the chain would fall onto the small chainring when the lever was still 45 degrees away from hitting the stop. That way, they could easily shift both levers at the same time with their right hand.

Some company, Shimano or Suntour (can't remember which), actually designed that 45-degree angle into one generation of their downtube front shifters.

I wish I'd thought of leaving my Campy rear derailleur's cable slack enough to do the same. My thumbnail eventually wore through the paint on my Bianchi Specialissima and into the chrome underneath.

No. It would be more responsive, however.

That's not my experience.

How could it not be? There is no reason at all that the shift lever should move even a millimeter before moving the derailleur.

Why would a friction shifting system need a barrel adjuster? If things are so out of order, check limit screws and tighten the cable. Am I missing something?

In the business, we used to say that cables stretch. It's not true, but they behave as if they stretch. Housings compress, and they also settle into their cable stops. This results in cables becoming loose. It's not a big deal unless it's annoying. You may want your derailleur to come out of high gear as soon as you move pull the lever. Or maybe the lever pulls a lot of cable to get to low gear but you run out of cable. A barrel adjuster effectively lengthens the housing which then effectively shortens the cable.

Back in the last century, we used to use friction RDs with click shifters sometimes.
An easy way to tweak the adjustment was to add a adjuster to the RD.
Just drill out the cable stop bottom on the RD and thread it for an adjuster.

SunTour is the only one that comes to mind.
https://www.velobase.com/CompImages/...C5CD2251B.jpeg

Agreed.

Update - it is def the shift lever working loose at folks suggested. Goes away after tightening the D-ring and then gradually loosens up. I will try the blue loctite. If that doesn't work will try one of these other suggestions. By crushing the D-ring threads you mean simply squeezing the D-shape smaller? or do you mean using vicegrips to simply tighten more than would be possible by hand?

I think he means to crush the threads a little to make them rougher so it catches and is slightly harder to turn.

Ahh Okay now I understand Thanks

I just went and looked at my Mavic... yup, there's an adjuster barrel.

N through Z, you're on your own.

Edit... might have originally been indexed.

Add split washer
 

I would add a 5mm split washer on the threads of D ring as well as the loctite. I would not do the vice grip on the threads hack.