Why XAVC files suddenly upload without video but good audio

I just had this happen (April 7 2025) on my M1 iMax running Sequoia 15.4. I shoot XAVC 4K on two Sony cameras and upload to FCP. Been doing this for years no problem. Last time I did it was around March 10 with no problems. I tried on April 7, and nothing but problems. Was having problems even copying the card to a hard drive in the finder. FCP wasn’t even running. When I finally was able to copy it, I would go into Import in FCP and even the Preview track would show black. A full upload would result a black screen and good audio. Much experimenting for two days ... and it’s any XAVC footage that I have ... even old stuff that I know transferred and uploaded OK in the past ... but it will not do it now. Tried cards from both cameras and on 4 different computers in 2 locations ... 2 M1 iMacs and 2 Intel iMacs. None worked.

One bizarre twist ... sometimes ... not all the time ... when I navigated to the folder in Import, all the clips would be duplicated in the Preview Window.  If I had 10 clips, there would be 20 clips. The first 10 would not have any video, the second 10 were fine and uploaded OK. But I could copy the same card immediately again, and there would be only the 10 bad clips. All the video plays fine in the camera. I had a deadline this week and couldn’t devote my full attention to this ... so I’ll be running more organized tests over the weekend, and then contact Apple next week. 

From my last successful upload on March 10 till now, I did the update on March 27 for Pro Video Formats 2.4 and the FCP update to 11.1 on March 30. No XAVC issues on March 10 … nothing but problems now.