WORKAROUND:
1. Backup the file {Diagnostic Server dir}\Agent\bin\SpotlightDiagnosticServer.ini into a different directory
2. Edit the file
3. Change "-Xmx4096m" to "-Xmx8192m"
4. Save the file
5. Restart the Diagnostic Server service
STATUS:
A fix is available in the latest version of Spotlight on SQL Server Enterprise which can be downloaded
here.