I found a bug in network scan. When connected to LAN and then switched to wifi sometimes your LAN connection stays in Device list and only thing can be don to delete it from there is to reinstall Avast.
You can connect do different network - scan it and scan will be ok. But if you connect back via WiFi to the network which you previously connect via LAN and WiFi you will still have LAN instance in the network even if it long time gone from router DHCP table, and you reseted your computer.