The IP address you see at the top of an asset page is the last IP address Lansweeper used to scan the asset, this is expected behavior. The other IP address should be visible in the network section of the asset page still though.
We're not sure which asset type you're talking about here, but all MAC addresses should be listed on the asset page as well in the network section. If the asset is non-Windows, the first MAC address scanned will be the unique key of the asset, as explained in
this article. Though this shouldn't be a problem when rescanning the asset through a different network interface.