MP4 files are not detected as video file but octet??

I uploaded five files the same day and in the same mp4 format exported from premiere with the same settings and to the same folder. Still three of them are now in octet format and two are mp4 videophiles. This makes no sense. It's a big problem since we are sending work copies and masters to our clients via CC. We can't have them downloading the files and changing extention. This would make us look like amateurs.

Since CC can't identify the video files automatically there should be a way to do it manually.