This problem will only occur when scanning IP ranges, it will not occur when using other scanning methods such as Active scanning or Scheduled Scanning.
Lansweeper notices that x.y.com is a DNS and tries to get the netbios name of the domain. If all methods of doing this fail it will as a last resort just take the first part of the DNS (which is correct in most cases). There is an easy way to fix this, go to Configuration > Scanning Methods > Active Scanning and add the domain DNS and netbios. Active scanning does not need to be enabled for this, simply adding the domain and rescanning the IP range should do the trick.