Hey Seth! Apologies for the delayed reply. This is somewhat multi-faceted. Easel references the first workpiece in a project when creating project thumbnails.
Our engineers deployed changes within the last few weeks to correct some behavior with workpiece and project thumbnails for cabinet projects. Before these changes were released, newly nested workpieces wouldn’t generate automatically with thumbnails. New workpieces from the Cabinetmaker would also be added after the initial blank workpiece in Easel. With the first workpiece being blank and projects with un-loaded workpiece thumbnails, the project thumbnail will typically be the default Easel icon shown in the screenshot. The projects in the screenshot without thumbnails were actually older projects that had just been renamed before the recording, which is why they don’t have thumbnails.
You said your question was unrelated to cabinet projects though. Most/all of my recent projects are cabinets, and the handful of my non-cabinet projects from recent months look okay. Could you share a screenshot of any examples of this behavior that you see with your own projects? Going back into the project to remove any blank workpieces and click through any workpieces that don’t have thumbnails should resolve these workpiece and project thumbnail issues for cabinet (and even some non-cabinet) projects.