SqlSetup: Exit codes from setup process are not trustworthy

Details of the scenario you tried and the problem that is occurring:
Currently there is no check for what exit code the setup process exits with.

In PR #578 it adds (when merged) reporting of exit code to the verbose logs when setup process exits. Also added so it catches exit code 3010 (see issue #565) so it writes a warning that reboot is required (partly fixes #565).
Thus I expected exit code 0 to be 'Successful'. And maybe it is. I have not been able to verify that.
And if exit code is anything but 0 and 3010 it will throw an error saying that setup failed, and check the summary,txt log file.

Well, it seems it wasn't quit that simple. I'm getting strange exit codes. Sometimes I get exit code is that sometime the exit code -2061893627 when the summary.txt file says exit code 3010. But most of the time I get the correct exit code 3010 from the process (which is correct).

I can't find any documentation around exit codes from SQL Server setup.exe.

The DSC configuration that is using the resource (as detailed as possible):

xSQLServerSetup 'InstallSQL2016'
{
    InstanceName = $Node."$($currentSqlInstance)InstanceName"
    Features = $Node."$($currentSqlInstance)InstallFeatures"
    BrowserSvcStartupType = 'Automatic'
    SQLCollation = 'Finnish_Swedish_CI_AS'
    SQLSvcAccount = $SqlServiceCredential
    AgtSvcAccount = $SqlAgentServiceCredential
    ASSvcAccount = $SqlServiceCredential
    SQLSysAdminAccounts = 'COMPANY\SQL Admins', $SqlAdministratorCredential.UserName
    SourcePath = $Node."SourcePath$($currentSqlInstance)"
    UpdateEnabled = 'False'
    SuppressReboot = $false
    ForceReboot = $false
    SourceCredential = $SqlInstallCredential

    PsDscRunAsCredential = $SqlInstallCredential

    DependsOn = '[WindowsFeature]NetFramework35','[WindowsFeature]NetFramework45'
}

Version of the Operating System, SQL Server and PowerShell the DSC Target Node is running:
Windows Server 2012, SQL Server 2016, WMF 5.0

What module (SqlServer or SQLPS) and which version of the module the DSC Target Node is running:
n/a

Version of the DSC module you're using, or 'dev' if you're using current dev branch:
Dev

Start at the SqlSetup setup-process exit-code handling and compare the process result with the SQL Server summary.txt exit code, including 3010 and -2061893627. Done should mean the resource reliably interprets the setup result and reports success, reboot-required, or failure consistently.