I have disabled debug mode, and I have tried adding the following to wp-config.php:

ini_set(‘post_max_size’, ‘500M’);
ini_set(‘upload_max_filesize’, ‘500M’);
define(‘WP_MEMORY_LIMIT’, ‘128M’);
ini_set(‘memory_limit’, ‘128M’);
ini_set(‘max_execution_time’, ‘300’);

I also tried adding

php_value session.gc_maxlifetime 10800
php_value max_input_time 10800
php_value max_execution_time 10800
php_value upload_max_filesize 110M
php_value post_max_size 120M

to .htaccess, and I still get the same issue.