I noticed an odd occurrence on the latest tracks. One of the listed tracks (Morning Dawn TM2) had no screenshot icon where a gray or black icon normally is to show if the course has a custom thumbnail or not. Likewise, hovering over the entry does not display the thumbnail, though the track page does have one (it is not a custom thumbnail).

Quick update, it looks like the icon has returned. I still have no idea why it was missing for a while...

Very strange.