Regarding:

    E: pymdown-extensions source: source-is-missing docs/theme/assets/pymdownx-extras/extra-loader-5bb526e4.js
    E: pymdown-extensions source: source-is-missing docs/theme/assets/pymdownx-extras/material-extra-3rdparty-69a692a6.js
    E: pymdown-extensions source: source-is-missing docs/theme/assets/pymdownx-extras/material-extra-theme-7c147bb7.js

upstream provided explanation in

    https://github.com/facelessuser/pymdown-extensions/discussions/1726

and in particular in

    https://github.com/facelessuser/pymdown-extensions/issues/1536#issuecomment-998045994

that the source files for this compiled/minified JavaScript files are in

    docs/src/js
    docs/src/scss
