I would go a bit further to solve this.
Remove the cups and have the headset faced - top and bottom surfaces milled to parallel.
This grade of steel frame would not have had this done at manufacture.
Once parallel, all pieces should line up for smooth(er) operation.
Loose balls over retainer will also add more bearings and points of contact -
a good thing in my opinion.

Curious if this french headset has the mysterious floating top cup?