HTTP header, HTML source and rendered page disagree

Checks

• Indexing instructions differ between sources robots_directive_differs
• Preferred address differs between sources canonical_differs
• Title or description changed by a script title_or_description_changed_by_script
• Language links differ between sources hreflang_differs
• Language in header differs from page language content_language_header_differs_from_html_lang
• Same tag repeated with different values duplicate_tags_with_different_values

Findings

• The HTTP header, the HTML source and the rendered page give different values

What this relies on

The rendered value is what the owner sees and intends; crawlers that do not render get the other one.

How to verify by hand

Search Console URL inspection for the directive Google read; a person for the intended value.