Since the changed were made that one can start the rendering while preview rendering is running (which is a good thing) it can happen that Octane gets completely unresponsive. This happens when you have the "New Window" option selected and the rendering is shown in a new window or when you have "Image Editor" selected and Blender randomly chooses some other window than the one where the preview rendering is running to display the final result (happens occasionally). It also happens when "Keep Interface" is selected. So whenever the final rendering is started while the preview is still trying to get refreshed, Octane is gone and both the processes for Blender and the Octaneserver have to be killed manually.
So it would be great if the preview rendering could always be stopped before the final rendering kicks in to avoid that lockdown. I guess the prompt in previous versions was there for that reason. But maybe there's a prompt-free solution to that.