df (with options) leaves zombie process

OS = CentOS 7.3 If I try to run the 'df' command on this server with an option (e.g. -h -l) it hangs and leaves a zombie process. I cannot Ctrl+z out back to a prompt. If I run 'df' against specific mount points that are found in FSTAB the command works successfully (e.g. df /home). How do I go about troubleshooting this?