After download, use a checksum tool to match the MD5 hash (usually listed in the "Metadata" tab). If the hash doesn't match, the file is incomplete.
If you cannot find a high-quality version on the Archive, the series is officially available on these platforms: HBO Max / Max : The primary streaming home for the series. Sky Documentaries : Available for viewers in the UK. Amazon Prime Video chernobyl serie completa archive.org