Scroll to incorrect anchor position

When I click on a link for the first time from the top menu, you can see that the scroll does not go to the anchor but a bit above it. What is strange is that if you click again on another link after, the problem does not occur anymore. It’s only the first time you click.

I guess the problem comes from the sticky menu, which is transparent and not taken into account at first, but becomes real after a first click.

How can I have the scrolling position correct ?

Thank you for your help

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