WP Query Is_404 set to true for page 2 and above in custom page template

WordPress version: 5.7.8
PHP : 8.X

Website is using a custom theme with its own set of page templates.
In the URL provided, the page is using a custom page template and “paginate_links” was used to generate the pagination at the bottom of the page.
(It only has a page title and a custom page template – post content is empty)

There are no issue in Page 1. However, upon click on page 2 and above, the system is 301 redirecting to the first page.

It appears the issue arises from the “handle_404” function in the “WP” class when the system is determining the value for $content_found.

E.g. URL : /course-search/2

After calling “WP Query” : “parse_query” function
– is_singular/ is_page : true
– is_404 : false
– post_content : “”

In “WP” : “handle_404” function, it was looking for the “<!–nextpage–>” substring to determine that content does not exceed max no. of page. However, since there are no post_content in the page, $content_found will be set to false.

This causes the is_404 parameter to be set to true in the “WP Query” object.

As a result, “redirect_canonical” is not processing the request as intended.

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