Read more tag bug causes loading error single.php

Hi,

The more tag causes a problem in posts loading from single.php.

This is the code I use:
<?php the_content('more','',''); ?>

I have upgraded to 2.6.5 for days ago, nothing seemed to be wrong until now. When the more tag is used in a post, it only displays correctly the first part of the post on the frontpage, but after clicking the singlepost it breaks the_content directly after the_title. This is the bottom code, after the title it gives an error:

<div class="postbody_singlepost">
<h1><a href="https://test.com" title="Lorem">Lorem</a></h1>
<div class="the_content">

So the whole content is not loading in single.php if the more tag is used. Could this be a 2.6.5 bug?
Not resolved the problem:
Disabled the more tag with php global
Switched theme
Disabled all plugins