Some MOV files imported to Final Cut Pro X 10.7.1 missing video and/or audio

Hi, I've recently imported MOV files to FCPX 10.7.1 on MacOS 14.5, from my iPhone running the Blackmagic Cam App and my Leica SL2. Most of my files import correctly, but about 10% of them are blacked out with no audio of video. A few of them have audio only, and no video. The video is just black, both in the media tray and in the timeline. The MOV files play fine in Quicktime (video and audio) and they work perfectly when imported into Davinci Resolve (video and audio).

Any suggestions?

Thank you!