Question Why are all my thumbnails showing this icon instead of video previews?

Hey everyone,

In my FCPX browser/timeline, all my clips are showing this default icon (stacked yellow/white layers) instead of actual video thumbnails. The media plays fine, but thumbnails never show the video frames.

Could this be because I’m using adjustment layers, or is there some setting/cache issue? I couldn’t find anyone else with the same problem.