File explorer unresponsive (3.6.5)

I am intermittently unable to open files (PDFs, ePubs, etc.) and browse folders from MarginNote’s file explorer. When clicking on a file or folder, there is no response.

Clearing temp storage and defragmenting the database has no effect. Importing files through the “import” button, dragging folders into the window, and altering the contents of the ~/Library/Containers/QReader.MarginStudyMac/Data/Documents/ folder all have no effect.