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…...#=z2chjyOQrOBHt(List`1 #=zd04maSBOsEoG, Stream #=zhGZCK3QA$7Vf, PptxSaveOptions...#=zINuimrg=(Document #=zHVmFA6o=, Stream #=zhGZCK3QA$7Vf, PptxSaveOptions...