Roan,
Could you check a couple of things on the problem PC:
1. Which exact keyboard layout is set for French? Windows offers a few variants (e.g. "French", "French (Belgium)", "French (Canada)" or "French (Switzerland)") - please check under Settings > Time & Language > Language & Region, or Control Panel > Language, and me us know the exact name.
2. Do you have any additional software installed that hooks into keyboard input? For example, keyboard remapping tools, macro utilities, clipboard managers, or specialized input software.
P.S. Denis, thanks for your comment!