FCPX No Picture when Sharing?

Hello All-

I have a short reel I have thrown together for an actor. A lot of our footage is 4K, while some of the other footage she brought in is "DX50", MPEG Layer 3? It was ripped from the internet...

Everything plays okay in the timeline, but when I export, I get full sound, but no picture. I've tried exporting with Project Properties set in 1080p, 720p, and 4K.

I also tried doing a "video only" ProRes 422 HQ share, and that shows vieo until about half way through the video, and then the screen turns black.

Any ideas on what could be happening here or how to fix it? I am just trying to export to a shareable and HQ file (.mov)?

Thanks