Font displays incorrectly unless in a private session

My own webpage displays incorrectly when I load it with Firefox, unless I am visiting with a private window. The page: https://www.coudert.name/publications.html The webfont is Satoshi, and Firefox does load it, but variants do not affect it (bold or italic, for example). All other browsers render it correctly. Firefox on my macOS laptop renders it correctly only in a private window, but not in my normal browsing session. There, it loads the font correctly, but does not apply bold or italics. Compare the difference between the two screenshots. I have no idea where this can come from. How to investigate? I have checked font-related settings and not found anything of note.