"SyntaxError: Unexpected token" error on l10n-js files
Finally located the source of the problem. Every page on the site included a widget in the footer using an HTML snippet for a CiviCRM sign-up form. The HTML snippet, despite being the one generated by the profile, was incorrect, and included a reference to an admin URL for a script, which wouldn't be accessible to non-logged in site visitors. Removing it resolved the issue.