It seems to me that WP Super Cache expects config files to be writable all the time, even if configuration is correctly set. It's not feasible that config files are allowed to be writable in production websites all the time (even after initial setup).
This is the message I get when write permissions are removed from
Reproducible in plugin versions 1.3.2 and 1.4.
Warning! Could not update /my/domain/public_html/wp-config.php! WPCACHEHOME must be set in config file.
Warning! /my/domain/public_html/wp-content/advanced-cache.php does not exist or cannot be updated.
1. If it already exists please delete the file first.
2. Make /my/domain/public_html/wp-content writable using the chmod command through your ftp or server software. (chmod 777 /my/domain/public_html/wp-content) and refresh this page. This is only a temporary measure and you’ll have to make it read only afterwards again. (Change 777 to 755 in the previous command)
3. Refresh this page to update /my/domain/public_html/wp-content/advanced-cache.php
If that doesn’t work, make sure the file /my/domain/public_html/wp-content/advanced-cache.php doesn’t exist:
1. Open /my/domain/public_html/wp-content/plugins/wp-super-cache/advanced-cache.php$wp_cache_file in a text editor.
2. Change the text CACHEHOME to /my/domain/public_html/wp-content/plugins/wp-super-cache/
3. Save the file and copy it to /my/domain/public_html/wp-content/advanced-cache.php and refresh this page.
Cannot continue... fix previous problems and retry.