It is happening for a while that when I want to drag a clip with its linked audio to a new track only the video is moving and the audio stays in the original track having to drag the audio separately. It is not that they are unlinked. I can move the video horizontally and the audio follows the video. It is in the action of moving the clip to a new track when the audio stays. And yes, I have ensured that there's an empty audio track under the video track I want to move the video to. I don't remember to have this kind of behaviour time ago.
Carlos, even though the events (what Vegas calls a clip) are grouped together, you still have to highlight (click and shift+click) both of them. Only then can you drag both the audio and video events to new tracks.