Hi Sergei Shibanov,
PFB my answer of your queries.
Is it possible use only first two lines for reproduce issue?
Answer- Yes
Answer - htmlString as read html from file as string and pass it, which I have shared.
Htm…...Services.PdfExport.PdfTemplateLoader...template) in /src/services/CI.DataAggregation/Services/PdfExport/PdfTemplateLoader...