Project Corruption: Black Spots Appear When Project Opened

This project has behaved consistently for the past 2 weeks, but today I opened it and found that my footage has these black flickering spots all over it in the timeline. Also, other XAVC footage suddenly plays at only 8FPS where it used to play smoothly before. Something broke, but I don't know what it is.
In addition, when I pause playback the footage appears to drop to 1/4 resolution.
Curiously, the spots don't appear in the Fusion page, but playback is impossible. Footage just won't play anymore.
In addition, when I pause playback the footage appears to drop to 1/4 resolution.
Curiously, the spots don't appear in the Fusion page, but playback is impossible. Footage just won't play anymore.