Support Forum

have you checked the server error log?  or your forum - toolbox - error log page?  might be running out of memory or other...

a link to site might help too...

well, its behind a paywall, so cannot really see...

but must be some sort of server configuration if it loads sometimes but not others...  like I said, maybe memory or cpu time...

perhaps try adding this to your wp-config.php file:

define('WP_DEBUG', true);

and when it happens, see if more data is recorded to the screen...