Issues importing new videos: only audio

I am having issues importing new video files (generally mp4) into Premier projects and placing them on the timeline. When I drag it as I would usually place it in, it will only import the audio and no video.

Initially I had though it was because I had different frame rates but it continues to happen with clips that are the same in frame rate, resolution, and codec. I have even put them through AME with the same settings.

For some reason, however, it does allow me to import entire clips when I drag them as a stack into a new project timeline.

At this point I'm not really sure what to do. Am I doing something wrong?