after upgrading to WordPress 4.6 got problems

Sounds like you need to increase your server memory limit. Several ways to do this.

1. If you have access to your PHP.ini file, change the line in PHP.ini
If your line shows 32M try 64M:
memory_limit = 64M ; Maximum amount of memory a script may consume (64MB)

2. If you don’t have access to PHP.ini try adding this to an .htaccess file:
php_value memory_limit 64M

3. Try adding this line to your wp-config.php file:
Increasing memory allocated to PHP
define(‘WP_MEMORY_LIMIT’, ’64M’);

4. Talk to your host.

Adding memory was first that i try – no matter how much memory i has added – result was the same. Didn’t help.

@benjaminbradley

268435456 bytes = 256 MB

The iTSec plugin Database Backup and File Change Detection features will set the minimum memory limit to 256 MB if less than 256 MB is detected.

ITSEC_Lib::set_minimum_memory_limit( '256M' );

dwinden