Add node fails with Attempted to read or write protected memory error

Recently I had worked on an issue where the end user was trying to add a third Node to an existing 2 node cluster. Soon after the setup is intiated, it would fail with the following error message (snippet from the Summary.txt).

Exception type: System.AccessViolationException
    Message: 
        Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
    Data: 
      DisableWatson = true
    Stack: 
        at Microsoft.SqlServer.Chainer.Infrastructure.MsiNativeMethods.MsiOpenPackageEx(String szPackagePath, UInt32 dwOptions, UInt32& hProduct)
        at Microsoft.SqlServer.Configuration.MsiExtension.InstallPackage.SetCommonProperties()
        at Microsoft.SqlServer.Configuration.MsiExtension.InstallPackage.RunMsiCore(String commandLine)
        at Microsoft.SqlServer.Configuration.MsiExtension.InstallPackage.RunMsiWithRetry(String commandline)
        at Microsoft.SqlServer.Configuration.MsiExtension.InstallPackage.RunMsi(IEnumerable`1 commandLineProps)
        at Microsoft.SqlServer.Configuration.SetupExtension.MSIInstallerEngine.InstallPackage(PackageId pkg, InstallAction pkgAction)
        at Microsoft.SqlServer.Configuration.MsiExtension.PackageInstallAction.Execute(String actionId, TextWriter errorStream)
        at Microsoft.SqlServer.Setup.Chainer.Workflow.ActionInvocation.ExecuteActionHelper(TextWriter statusStream, ISequencedAction actionToRun)

“Attempted to read or write protected memory. This is often an indication that other memory is corrupt.” Scary little error message! Since this is a setup related issue, the best place to start troubleshooting it is from the Setup Logs.  This article has more details on how to read SQL Server Setup logs.

Detail.txt pointed in the right direction as seen below.

Opening existing patch 'c:\Windows\Installer\97363c.msp'.
Couldn't find local patch 'c:\Windows\Installer\97363c.msp'. Looking for it at its source.
Resolving Patch source.
SOURCEMGMT: Looking for sourcelist for product {D7C6A337-F6BB-46CB-AE32-204DD6A8825D}
SOURCEMGMT: Trying source c:\7cb5fee2d4775f9d53c7f95659\x64\setup\.
Note: 1: 2203 2: c:\7cb5fee2d4775f9d53c7f95659\x64\setup\sql_ssms.msp 3: -2147287037 
SOURCEMGMT: Source is invalid due to missing/inaccessible package.
Unable to create a temp copy of patch 'sql_ssms.msp'.
Searching provided command line patches for patch code {D7C6A337-F6BB-46CB-AE32-204DD6A8825D}
Could not find source for missing patch {D7C6A337-F6BB-46CB-AE32-204DD6A8825D} -- orphaning this patch
SequencePatches starts. Product code: {72AB7E6F-BC24-481E-8C45-1AB

Now it was very clear that the issue is the classic missing MSI/MSP file issue. It was just matter of copying the right files to C:\Windows\Installer as explained here and here.

Once the missing files were replaced, the setup completed without any further errors.