When a network asset is being scanned, Lansweeper needs to determine whether or not the asset is already present in the Lansweeper database. It does this by comparing the "unique key" or "internal ID" of the asset. Assets with the same "unique key" or "internal ID" will be merged into the same Lansweeper web page. Assets with a different "unique key" or "internal ID" will have separate Lansweeper web pages.
More information can be found here: https://www.lansweeper.com/kb/149/how-lansweeper-uniquely-identifies-assets.html
In most cases, the easiest way to prevent duplicate assets when using multiple network cards, is adding an exclusion for the other IP addresses. You can find more information about excluding here: https://www.lansweeper.com/kb/99/excluding-assets-from-scanning.html