epub and mobi rendering problem

[pstrg]

I note two problems with epub and mobi rendering:

1. Sometimes (not always) font size isn't respected: parts of the text that should be displayed with a smaller font are not (however, both Sigil, which was used to edit it, and Kindle do display them correctly) - please see image:
   https://ibb.co/sPXWQ8k
2. Sometimes (not always) the index does not display at all (again: checked OK in other environments.)
   Is it perhaps because SumatraPDF's html rendering engine is picky?

[GitHubRulesOK]

Currentl I cant edit your question but can post your image

The rendering engine in current 3.4 pre-release has been standardized to using MuPDF for rendering, so most ePub books will look significantly different but mobi/aws files may still use the older renderer. Thus I have to suggest you try a current portable copy from https://www.sumatrapdfreader.org/prerelease (keep your old one, until you decide to switch totally, I have both but installed is the current pre-release)

[pstrg]

Current pre-release build (version 14255) renders as expected - both body and index.
Thank you.