Thanks for your report.
I have sent you an email with a development version of WinSCP to address you have used to register on this forum.
I have two VBScripts using WinSCP .NET automation objects which are started nearly at the same time.
Each scripts gets a couple of files using
"set WinSCP_TransferOperationResult = WinSCP_Session.GetFiles(RemotePath, DESTFOLDER)"
in a loop.
Both scripts abort with an error in System.Xml like "The 'group' start tag on line 54 does not match the end tag of 'download'. Line 57, position 7."
Reason: WinSCP writes a temporary xml file in the TEMP folder with information of each file transfer of the session and its result. Unfortunatelly both scripts are using the same temporary file mixing up their output and damaging the XML structure.
Using WinSCP 5.1.1 with WinSCP .NET Assembly and .NET Framework 2.0 on Windows Server 2008 R2