Same Issue: Clips go black

I'm having the same issue with clips going black in FCPX bins and the timeline. I'm using 10.7.1 on a MacBook pro running MacOS Sonoma 14.4.1. And i've seen this on my older Mac at home, an iMac 5K 2017 running the same FCPX version. I can highlight the black clips to reveal in the finder, drag them each to their spot on the timeline and no fix. Same for dragging from the finder to the bin. No go. I've deleted the event, restarted FCPX, killed the preferences, made a new event and imported the clips from my external drive and I can watch in real time several just go to black. Odd! I'm beginning to think this is an OS problem and not FCPX. Reason being, I can export a FCPXXML, go into Davinci, open the xml and relink all the clips and they won't re-connect. Stay black and media offline errors. The clips are all shot on iPhone 12 and 11 as most compatible MP4. A few are BlackMagic app .MOV files. Would love some help with this one. I've not had Apple software problems since the original final cut.