Backup 12.5 Console Server Error code 100011

I fought this error for the better part of 5 hours across the course of 2 days:

Internal Server Error code 100011

The error was displayed when browsing to the Console Server > Settings > System Settings.

The issue is related to disabling IPv6 but leaving any IPv6-related entries in /etc/hosts.

E.g., remove or comment out the :: line as shown below:

[jeffy@acronis ~]$ cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

==>

[jeffy@acronis ~]$ cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
#::1         localhost localhost.localdomain localhost6 localhost6.localdomain6

Hopefully this helps you avoid my frustration.