CF is crashing our websites

Seems like every week we get this message on one of our sites, then have to change the CF folder via FTP, then delete CF and reinstall. Then it is okay… until a week later another site has the same problem. What’s up? Here is the message we get:

Fatal error: Uncaught Error: Call to a member function get_author_permastruct() on null in /home/customer/www/ Stack trace: #0 /home/customer/www/ get_author_posts_url(‘0’) #1 /home/customer/www/ CF\WordPress\Hooks->getPostRelatedLinks(801) #2 /home/customer/www/ CF\WordPress\Hooks->purgeCacheByRelevantURLs(801) #3 /home/customer/www/ CF\WordPress\Hooks->purgeCacheOnPostStatusChange(‘publish’, ‘new’, Object(WP_Post)) #4 /home/customer/www/ WP_Hook->apply_filters(NULL, Array) #5 /home/customer/www/leavebehindab in /home/customer/www/ on line 347