I'm not sure if this is the exact problem I have had recently, but if it is, it is an easy solution. I was working in a project and went to drag a clip in that I normally add to the end of videos (it's an mp4 tag), but only the audio was showing up. I did a work around that wasn't idea and then it happened again in a new project from camera footage I was trying to drag in today. So I took a nap. When I came back, I saw the first A1 box was clicked in the timeline on my first clip. When I unchecked it, I was able to drag in any clip as I normally did. Weird that in years of using Adobe that has never happened before. You can see in the photo when the A1 left of the lock is checked the new clip on the end only came in with the audio. Unchecked, it comes in with both audio and video.
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