final cut pro x won't let me import some files

It looks like the transfer was not completed.

I see files up to IMG_9949.MOV that seem fine, and all starting from 9950 are zero bytes.

Look at the files on your iPhone to confirm and, if necessary, transfer them again.

I'd connect the cable between your iPhone and your mac instead of using AirDrop.

Open the clip in Quicktime Player and press Command-I. Post screenshots.

If it does not open in Quicktime Player, open in VLC and likewise press Command-I.

One other crucial thing: does FCP have Full Disk Access in System Preferences->Security & Privacy->Privacy? It must.

What version of the OS and FCP are you using? Did these clips come from an iPhone? Can you open a clip in the QuickTime player? What does it say in the QT inspector window?

Can you open one of the clips in the QuickTime player? The inspector window is in the QT application. It looks like the files are on an external drive. How is that drive connected and formatted?

You can’t open the dimmed files in the QT player? Try VLC and go to the information window and give details on what you see. Try to convert the files in the Finder?

These files show up as having zero bytes.

No idea how they came to be, but it is safe to just delete them.

Don’t know what they are, but they have no size and were all created at the same time.