"Encode Selected Video Files" renders only first frame of video.

In the finder, I hold the control key and click on the file, and from the popup menu I select Services -> Encode Selected Video Files. I select 480p, "Greater compatibility." It says the format will be H.264/AAC. I click Continue. The .m4v file it produces is about 1/4 the size of the .mov file, and plays the right audio, but the visual is just the first frame for the entire length of the video.

This happens in 720p as well but not 1080p. My original file is a 1080p H265 footage shot on a Fuji XT3.