The Velo-Orange metric headset wasn't very well thought out! It's actually a disservice to many customers!
The problem is the V-O headset has a stack height of 41mm which was the standard for Campagnolo, Stronglight S7 Super Competition and other "Professional Quality" headsets.
Far less than 5% of all of the French bikes ever used those headsets!
Most steerers on French bikes are too short for the V-O headsets, thus the problems that you encountered!
How stack height is measured:
How to measure the steerer length:
The Stronglight P3 model with a 33mm stack height were the most commonly used headsets on better quality French bikes from the 1950s through the 1970s, also, the most frequently in need of replacement!
Lightrace and a lot of other French headsets had stack heights of 28-33mm.
The less common Stronglight V4 Competition headsets with a 38mm stack height rarely needed replacing because of their design.
Stronglight A9 needle bearing alloy headsets were used on a lot of better French bikes during the 1980s. They had a stack height of 38mm too but they're pretty bullet proof and don't need to be replaced very often.
Tange used to make French size headsets that were perfect replacements for most French bikes.
There's a trick that works great for replacing a French headset.
It's usually only the bottom cup and fork crown race that needs replacing because of wear and indentations (indexing).
Tange makes Inch size headsets with a 27mm crown race that will fit French forks without any modification.
Use the bottom components with the old French top components and voil?, you have a better than new headset that looks original!

Chas.
SF Bay Area, CA USA
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1984 Criterium
1969 TdF
1971 TdF
1974 TdF
1984 TdF x 2 Bikes
1970 SC
1971 SC
1972 SC
1984 SC
1984 Team Pro
1985 Professional
1990s Team Replica