Repeated errors

Hi I have posted on this subject before and managed to fix it using your kind help thank you, but unfortunately this keeps happening and I keep having to fix it so it really needs a permanent solution.

Randomly I try to access the site and I get this message:

Warning: require_once(/home/absol832/public_html/BestInWorthing/wp-content/themes/DT/framework/class/class_core.php): failed to open stream: Permission denied in /home/absol832/public_html/BestInWorthing/wp-content/themes/DT/framework/_config.php on line 52

Fatal error: require_once(): Failed opening required ‘/home/absol832/public_html/BestInWorthing/wp-content/themes/DT/framework/class/class_core.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/absol832/public_html/BestInWorthing/wp-content/themes/DT/framework/_config.php on line 52

As I say I know now how to fix it but there must be something fundamentally wrong for it to keep happening – please advise

Thanks in advance
Jan