Exchange 2013 CU12 failed to install error 1619

This has got to be the dumbest thing I've ever come across when dealing with Microsoft products.
When installing CU12 for Exchange 2013 last night, the setup failed and was presented with this error:

Configuring Microsoft Exchange Server

Language Files COMPLETED

Restoring Services COMPLETED

Language Configuration COMPLETED

Mailbox role: Transport service COMPLETED

Client Access role: Front End Transport service COMPLETED

Mailbox role: Client Access service COMPLETED

Mailbox role: Unified Messaging service COMPLETED

Mailbox role: Mailbox service FAILED

The following error was generated when "$error.Clear();

Install-MsiPackage `

-PackagePath ([System.IO.Path]::Combine($RoleLanguagePacksPath, "Setup\ServerRoles\UnifiedMessaging\MSSpeech

_SR_TELE.ca-ES.msi")) `

-PropertyValues ("ARPSYSTEMCOMPONENT=1 ALLUSERS=1") `

-LogFile ([System.IO.Path]::Combine($RoleSetupLoggingPath, "InstallSpeech-ca-ES.msilog"))

" was run: "Microsoft.Exchange.Configuration.Tasks.TaskException: Couldn't open package 'C:\Program Files\Microsoft\Exchange Server\V15\bin\Setup\ServerRoles\UnifiedMessaging\MSSpeech_SR_TELE.ca-ES.msi'. This installation package could not be opened. Verify that the package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer package. Error code is 1619. ---> System.ComponentModel.Win32Exception: This installation package could not be opened. Verify that the package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer package

--- End of inner exception stack trace ---

at Microsoft.Exchange.Configuration.Tasks.Task.WriteError(Exception exception, ErrorCategory category, Object target,Boolean reThrow, String helpUrl)at Microsoft.Exchange.Configuration.Tasks.Task.WriteError(Exception exception, ErrorCategory category, Object target)at Microsoft.Exchange.Management.Deployment.InstallMsi.InternalBeginProcessing()at Microsoft.Exchange.Configuration.Tasks.Task.<BeginProcessing>b__5()at Microsoft.Exchange.Configuration.Tasks.Task.InvokeRetryableFunc(String funcName, Action func, Boolean terminatePipelineIfFailed)".

The Exchange Server setup operation didn't complete. More details can be found in ExchangeSetup.log located in the

<SystemDrive>:\ExchangeSetupLogs folder.

PS D:\Install\CU12>

I started the install with extracting the setup files to D:\Install\CU12, then ran the following command:

.\setup /mode:upgrade /iacceptexchangeserverlicenseterms

Looking in the exchangesetuplog file I saw that setup was looking for the missing file in this folder:

C:\Program Files\Microsoft\Exchange Server\V15\bin\Setup\ServerRoles\UnifiedMessaging\

Strange, because thats not where I extracted the setup files.

So copied the setup folder from the extracted folder:D:\Install\CU12 to C:\Program Files\Microsoft\Exchange Server\V15\bin\ to make sure the setup folder with install files where there, then started the install again from the D:\Install\CU12 folder and the everything went fine and without a glitch, I even think that it was a little bit faster. But maybe that's just wishful thinking because it was at 01:30 in the night....

According to this post from Peter de Tender I'm not the first to witness this, and sure as hell won't be the last.