FCP won't render all of the smooth slow-mo parts of my project

There are a few sections in my FCP project that show as unrendered in the timeline, and those dotted lines won't go away, no matter how many times I select "Render all" or "Render selection." I'm looking at the task manager, and sometimes I can force it to start working, and the dotted lines start to disappear from the timeline... but then they reappear, and the task manager goes back to showing "idle." I think the unrendered parts are all slow motion parts.

I thought maybe exporting my project would force it to finish rendering, but instead it gave me this error prompt that my project has background tasks that are not yet complete. And as you can see in the attached, it's indicating that all background tasks are idle.

FYI, this issue started happening after I moved my project to a new library.