pfSense

In "DHCPv6 Server / DHCPv6 Options" PD Range To/From differs.
Form IDs != $_POST IDs

More specific:
"Form_Input('prefix_from', ..." does not work well with $_POST['prefixrange_from']
Likewise for prefix_to != prefixrange_to

This is easy to fix.

Suggested fix:
Rename prefix_from and prefix_to to prefixrange_from and prefixrange_to.
(Remember there are 2x occurences of prefix_from/prefix_to)

Reference:
https://github.com/pfsense/pfsense/blob/master/src/usr/local/www/services_dhcpv6.php