Bought Epub book is wrong on EPUB3 Reader

Hi there

I bought a book and downloaded it in epub format.

If I try to open it on Pocketbook era, the images, and code don't display.

If I open the original file through an old reader (EPUB2), everything is displayed, but the fonts are terrible (and the old reader lags).

If I convert it to FB2 format, the code is displayed, but the images don't show.

pandoc ./js.epub -o js.fb2

P.S. I read it like this all the time until I made an opening, which I wrote about later.
I used for it https://pandoc.org/

Solution:

If I convert it from EPUB to EPUB format,

pandoc ./js.epub -o js_copy.epub

then everything works in the latest reader.

I don't know what you use to convert Markdown to Epub but would be great if you would provide EPUB 3 initially

Thanks