Meta charset doesn't consistently respect French accents

Question

Environment: html website (no cms), local repo managed with visual studio, connected to an AzureDevOps staging environment. Meta charset defined as "utf-8".

Issue: If I paste French copy into a page, and compile the site (using yarn), accents don't render consistently, whether I scrub the text in notepad or not. There doesn't seem to be any rhyme or reason to the results.

I can copy a correctly rendered letter with an accent right from the browser, and that seems to work fine.