We certainley have exported ten thousends of files within the last 3 months. Because we digitaze tapes and vinyl for customers. Always with the latest version from Sonar on three computers.
But always without "64-bit Engine" and always with disabled plugins. But all other options are clicked.
That must be up to hardware or a misterious plugin. Some old versions from Waves don't work anymore since the 2 last versions from Sonar. Something has changed the last 2 versions. For a test I would try to delete all plugins.
But RESTART the project after you have deletet all plugins !!
If this doesnt work, it must be up to drivers or hardware.