Created Unassigned: AddComment: The required attribute 'authorId' is missing [15291]

I'm adding many comments into an excel file. Everything works fine in first edited sheet, but in second one EPPLUS doesn't store AuthorList :
<x:authors xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main" __/>__

and in comments it doesn't store authorId reference:
<__x:comment ref="B5"__ xmlns:x="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
<x:text>
<d:r xmlns:d="http://schemas.openxmlformats.org/spreadsheetml/2006/main">
<d:rPr>
<d:sz val="11" />
<d:rFont val="Calibri" />
</d:rPr>
<d:t xml:space="preserve">some text here</d:t>
</d:r>
</x:text>
</x:comment>