VAST-2.0-mediafiles-unknown-child
<MediaFiles> contains an unrecognised child element
ErrorSchemaIAB VAST 2.0 §2.4.1VAST 2.0 and later (all versions)
`<MediaFiles>` may contain `<MediaFile>`, `<Mezzanine>` (4.1+), `<InteractiveCreativeFile>` (4.0+), and `<ClosedCaptionFiles>` (4.2+). Other children are schema errors.
How to fix
Remove the unrecognised element from <MediaFiles> — valid children are <MediaFile>, <Mezzanine> (4.1+), <InteractiveCreativeFile> (4.0+), and <ClosedCaptionFiles> (4.2+).
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