The most likely cause for a Subset Sync job to fail is due to logon details defined within the RFC setup. Check the following details within the RFC:
(A) Ensure that the logon details are assigned with a dialogue (named) user (B) Ensure that the RFC destination does not have the 'Current User' option set
This screen capture shows the details of an RFC that has been defined within Qlik's systems.
It may be helpful for your organization to create all-new RFC's specific for Gold Client purposes.
Once any changes have been deployed, try the export again. Contact the Qlik support team if issues persist.