What I’ve done is a momentary fix that works within Nuendo 8.1.10 (Mac), Duplicate the Nuendo App, call it NuendoCopy or whatever you like. control-click on Nuendo 7 ( hopefully you still have it on your system) and select “Show package contents” click, Contends/Components and then copy the videoengine.bundle. Copy and replace it with the Video engine bundle of N8copy (same location but just that od N8). you do need system priveliges so have your password handy. Now ones you boot your Nuendo copy you should have to option available to replace audio in Vido under Export.