Navbar hides header on Firefox

[PGijsbers]

When loading a documentation page on a specific header in Firefox, e.g. usage#basic-usage, when coming from a different page, the navbar hides the section header.

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usage#basic-usage shows as:

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I expect usage#basic-usage shows as:

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The behavior seems to work correctly on Chrome. When moving between section headers on the same page, it also seems to work fine on Firefox.

I tried to apply this fix, but it did not seem to help (though I can't guarantee I did that right).

Using Firefox 66.0.3 (64-bit).