Hello. We need to exclude from scan “Full and Fast” config some usernames during (bruteforce / default account scan), because during the scan these usernames are locked out on a system. We tried to use custom credentials option but this didn’t have any affect. How can we do that?
Congratulation you found a Denial of Service Vulnerability within your target 
You can disable individual NVT / Families by cloning full and fast end change you scan-config for your individual needs.