FCPX 11.1.1 Project preview window suddenly went black

Running M2 MAX / macOS 15.5 (24F74) Sequoia / FCPX 11.1.1

I'm using Final Cut Pro X 11.1.1 and experiencing a frustrating issue. I built a project and everything was working fine—source files play normally, timeline thumbnails show up, and the clips preview correctly in the browser when I scrub over them.

However, the project preview window suddenly went black. Audio plays, but there’s no video. The timeline shows all the clip thumbnails, and the source clips themselves are fine, but the main viewer just shows black during playback.

I didn’t intentionally change any settings, so I’m wondering:

Could I have clicked something by mistake? Is this a known bug? Do I need to rebuild the entire project from scratch to fix this—or risk it happening again?

Any advice would be hugely appreciated. I’m on a deadline and need to deliver this project soon.