CAX 30 backup works but restore action shows 404 page and fails.

I have CAX30 Cable Modem & Router. 

I have two problems: 

1. I defined all devices on my network and blockes some of them in Access Control. Under Administration > Backup Settings, I backed up that configuration. Later on, I allowed all devices and saved that configuration as well. Finally, I tried to restore these settings but it shows me 404 error for both configurations. I can't restore at all. 

I also tried to open that window separately, but same result. The web page address is:   http://192.168.1.1/Restore_Md5Error.php

Please check the attached images. 

2. I also want to filter discord.com completely from my network, but Block Sites also does not work for me. Please check the attached image.