I had this problem and after tailing the errors logs on a Plesk server
tail -f /var/www/vhosts/domain.com/logs/error_log
I noticed mod_fcgid: read data timeout in 45 seconds, referer: followed by Premature end of script headers: upgrade.php, referer: to fix this issue you need perform the following commands
and change the timeout from 45 to something a little larger, lets say 600.
Why is this a problem?
In previous versions of vb, there’s a cron which should run and remove unused attachments, this has been broken the whole time resulting in large attachment folders. The idea is the cron will remove files with “0” views (which should now be fixed)
On version 4.2.4 a bug had been found which shows that some files were being marked as “0” when it shouldn’t this resulted in losing some files.