Ok, just tried with OctaneX from App Store, and you are right, it is limited in saving only .orbx scenes, no .ocs saving, if you force to save in .ocs, it will be saved as .ocs.orbx:
But there are no issues with Standalone PR11, you can find it by visiting your personal Downloads area:
https://render.otoy.com/account/download_archive.phpciao Beppe