I’m having the same problem
Warning: shell_exec() has been disabled for security reasons in […]/wp-content/plugins/backupwordpress/functions/backup.files.functions.php on line 133
The problem is in blocking the server, not in plugins.
Generally proxy or firewall. I have the same problem and talking to the guy who maintains the server, he told me about this type of lock. Do not know if in all cases, but in mine it is so, because the server is within the company. In short, he will not change.
Sorry for my bad English.
