Visual glitch from old asset virally infecting every project

This is weird one.  I'm doing an animation project, and in one scene, I drew this bird-beak asset. I started a new scene, entirely new project afterward, and this beak is constantly showing up in my viewer.

To be clear about my issue: the beak is most certainly not actually there. It shows up in the viewer preview, and sometimes during preview playback, but it doesn't show up in the export, and it's never in the same place in the timeline.  If I hide ALL layers, it disappears, but I'm 99.9% sure that beak is not in any of these layers.  It's not even in the project files anymore - I deleted the asset entirely!  So I'm reasonably certain it's some visual glitch in memory or something.

I even reduced my project to make sure, down to just a few files - no bird beak.  I purged the caches. I've restarted my computer and AE.  Still there. It appears in projects that share assets with the original project, like a virus that gets passed along (even assets unconnected to the actual bird beak). Example: I made a new project, imported that first video with the bird beak asset, so that I would have some of the same animations.  I reduced the project, got rid of the bird beaks, but it's still there. OK. Then, I make an entirely new project, again, import that second video's content - now the bird beak asset has never once been imported into this project - still, it's there, flickering on and off, sometimes hanging around, sometimes disappearing, sometimes it even animates along with other assets (like rotating with something else that is rotating. 

It's absolutely bonkers. I've never seen anything like it.  Any ideas?