Picture cannot be posted on Facebook Pages using byte arrray

[Schuyweiz]

I have followed the code example in the documentation and ended up with a Facebook error, which says, that
'Can't Read Files - Your photos couldn't be uploaded. Photos should be less than 4 MB and saved as JPG, PNG, GIF, TIFF, HEIF or WebP files.'
And yes, the file is within the restrictions given.
Moreover, when I do it through the InputStream method, it works (but it doesn't suit my needs this way).