The selection range in the image below is the iTXt Text field.
According to PNG Specification - iTXt [1], there should be exactly 5 null characters following the Keyword field [*].
However, there are 6 null characters, meaning the Text field begins with an unexpected null character.
We expected the Text field to start directly with
<x:xmpmeta...
, but instead it contains a leading null character.
Reference:
[1] PNG Specification - iTXt (https://www.w3.org/TR/png-3/#11iTXt)
Note:
[*] Expected null character breakdown:
  1. Keyword's null separator
  2. Compression flag (recommended as 0 for XMP)
  3. Compression method (recommended as 0 for XMP)
  4. Language tag's null separator (Language tag is empty, so only null separator is here)
  5. Translated keyword's null separator (Translated keyword is empty, so only null separator is here)