Since this question was also sent to our support team, I'll drop the answer here too for anyone having a similar issue.
When the same asset was rescanned on the new host, it was automatically merged with the old asset, resulting in only one computer. When a VMware host is scanned, Lansweeper collects a list of MAC addresses of its guests. This information is used to display the hostname on the guest's asset page. If both hosts have hosted this asset at one point, the asset will be in this list twice. When displaying the assetpage, Lansweeper will check the database for a link to a VMware host, and will display the first value it finds.
The way we currently gather the information, Lansweeper cannot determine which host is currently running the guest.