The last two times I have upgraded my scan server to the latest build the Lansweeper Server service has been slow to stop which causes the install to complain about a file being in use. Its not a big deal, if I kill the LansweeperService.exe process manually or wait for it to eventually stop then click retry the upgrade completes just fine. Today the locked file was C:\Program Files (x86)\Lansweeper\Service\GemBox.Spreadsheet.dll, I don't recall if it was different last time or not.
Thought I would pass it along, it feels like the timeout from the installer runs out before the service actually stops.