Cannot detach Video

I need to detach a video from an existing file for future use, but the video can’t be detached.
In the setup window I right-click on the flow panel, then I go to Video>Detach and click that option, but nothing happens and the video stays attached. How can I solve this?

Just found out that the video is detached as instructed, but the video offset information is still being displayed. This makes it appear as if the video is still attached. Deleting this info (i.e. all settings back to ‘0’) solved the issue.