Very strange wordpress circular redirect ERR_TOO_MANY_REDIRECTS, why?

Question

PHP

Good day!
Tell me what could be the reason for the cyclic redirect to WordPress pages.
And very strange... Because only on some records.
The main page and most pages work fine ( example ). But there are exceptions .
The htaccess file is clean (standard in the sense):

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

Previously, this was not the case, but then there was a sharp drop in traffic by 30% - I began to find out why this is happening here ...
Tell me, what could be the problem. Thanks in advance!

Answer 1

In general, I found a solution ... It's stupid and does not explain the cause of the error, but it works ... I
deleted the entry (from the trash too), created it again - it worked.
PS: Thank you Alexander Leonovich for your participation!

Answer 2

Has the source code changed before? The first thing that came to mind is that in your script you set the location header to the same script.