I opened the page https://www.wikidata.org/wiki/Q52083822 and it is showing Czech language for the page-content's section headings. My interface language is set to English, and if I switch to German (which works as expected) and then back to English it still shows the Czech headings.
I have purposefully not tried purging the page, in case that helps you reproduce/diagnose.
Addshore suggested it was probably related to page-cache getting mixed up somehow.
Other users are reporting the same problem, with other languages and items, at https://www.wikidata.org/wiki/Wikidata:Contact_the_development_team#Interface_language_bug
See T201170: Allow wikibase to render entities for an arbitrary target language, instead of the user's UI language for a complete solution.