You are interested in third party security vulnerabilities and run the Scan Based Full Audit target security history report. Under the 'Names' category, the report says 'Netbios name ... has been removed', and you would like to know whether this a vulnerability and how it can be fixed.
The Security History reports are meant to detail information retrieved from the last scan on the target machine. It will compare this to the previous scan results to determine changes that have been made regardless of whether this was done as a part of LanGuard remediation operations or not.
NetBIOS name is one of the System Information categories gathered by the normal checks in a full scan or vulnerability scan. It has all the NetBIOS name mappings gathered from the target machine cache. The message 'NetBIOS name ... has been removed' means that a particular NetBIOS mapping was removed from the target machine between the scans, but LanGuard has no details on which process removed it.
This is not a vulnerability, and there is no need to fix this. The security officers can analyze such changes during the incident investigations.