Large sections of documentation missing

## URL of the page

https://loopback.io/doc/en/lb3/Model-definition-JSON-file.html

## Nature of the issue

Missing content from the website documentation pages.

## Expected behaviour

All sections and content should be showing.

## Actual behaviour

In [the corresponding Markdown file](https://github.com/loopbackio/loopback.io/blob/gh-pages/pages/en/lb3/Model-definition-JSON-file.md) in the repo, all the sections and content look fine. However, on the corresponding HTML page, the section "[Exclude properties from base model](https://loopback.io/doc/en/lb3/Model-definition-JSON-file.html#exclude-properties-from-base-model)" is missing. Similar issues happen throughout many pages of the website.

Please fix this.

Compare the rendered page at loopback.io/doc/en/lb3/Model-definition-JSON-file.html with pages/en/lb3/Model-definition-JSON-file.md, starting with the missing “Exclude properties from base model” section. Trace the documentation build or rendering entry point that converts the Markdown into HTML, then verify that the section and other affected pages render completely.

Written by the indexing model from the issue text.