FTP Users Login Error when using ProFTPd: USER username (Login failed): Incorrect password.

If when using ProFTPd you see this error:

USER username (Login failed): Incorrect password

And, the /var/log/secure log shows:

proftpd: PAM unable to dlopen(/lib64/security/pam_stack.so): /lib64/security/pam_stack.so:
cannot open shared object file: No such file or directory

The solution is to replace the /etc/pam.d/proftpd file with the following: