D365FO: "Object reference not set to an instance of an object" error while updating 10.0.39 on local Hyper-V machine

There is a known issue when you try to update D365FO Hyper-V machine with 10.0.39 by installing new D365FO update. You may get "Object reference not set to an instance of an object" error during installation.

The solution is to run the following PowerShell code, then retry installation.

#set Dynamics Deployment folderpath in registry and create folder structure
$Installinfodir = "c:\Logs"
Write-Host "Checking InstallationInfoDirectry in registry for path $($Installinfodir)..." -foregroundcolor Yellow

if ((Get-ItemPropertyvalue HKLM:\SOFTWARE\Microsoft\Dynamics\Deployment -name InstallationInfoDirectory -ea 0) -ne $Installinfodir){
	write-host "Changing DynamicsDeployment folder path in registry to $($Installinfodir)..." -foregroundcolor yellow
	Set-ItemProperty -Path HKLM:\SOFTWARE\Microsoft\Dynamics\Deployment -Name InstallationInfoDirectory -Value $Installinfodir -Type String
}

@('HotfixInstallationRecords', 'MetadataModelInstallationRecords', 'Runbooks', 'ServiceModelInstallationRecords') |
    ForEach-Object {
    	if (!(test-path (Join-Path "$Installinfodir\InstallationRecords\" $_))){
        	New-Item (Join-Path "$Installinfodir\InstallationRecords\" $_) -ItemType Directory -force | out-null
	 }
}

More details here and here.