We have been having this issue for ages, and have even moved servers because we thought our last provider was doing something wrong. But the issue has followed us. We have observed this issue on at least 2 different sites, but it mostly happens to one specific site (our most important one of course). It happens at all times of day and with 2-3 weeks in between, sometimes only days. Last night it happened at 03:34 where I am 100% sure no one was working on it. But as said, it has also happened during the day
The bottom bit of our .htaccess file is changed from:
to
But the really weird bit is that it still shows as php 7.3 in both cPanel and WHM screens. Just now when checking I have realized that the two domain that it has happened on both have subdomain that use the older version of PHP so it is likely this is related.

To fix the issue, we set the site back to and older version and then back to 7.3 again. To re-iterate... the above does not change, only the .htaccess changes (when the problem happens).
Any help will be appreciated.
The bottom bit of our .htaccess file is changed from:
Apache config:
# php -- BEGIN cPanel-generated handler, do not edit
# Set the “ea-php73” package as the default “PHP” programming language.
<IfModule mime_module>
AddHandler application/x-httpd-ea-php73___lsphp .php .php7 .phtml
</IfModule>
# php -- END cPanel-generated handler, do not edit
Apache config:
# php -- BEGIN cPanel-generated handler, do not edit
# Set the “ea-php54” package as the default “PHP” programming language.
<IfModule mime_module>
AddHandler application/x-httpd-ea-php54___lsphp .php .php5 .phtml
</IfModule>
# php -- END cPanel-generated handler, do not edit

To fix the issue, we set the site back to and older version and then back to 7.3 again. To re-iterate... the above does not change, only the .htaccess changes (when the problem happens).
Any help will be appreciated.