All covers of a work not showing for all books

I got a bunch of duplicate ebooks yesterday, and when I added them, I also uploaded higher-res covers than previously. When I did so, I also pulled up my older copies and switched them over to the newer, better covers. Usually hitting "recalculate cover" a couple times or waiting a few minutes was all it took to make the new cover available for all copies. But two books remain that are unable to see the newer covers:

https://www.librarything.com/work/95127/covers/217464283 (8 custom covers available)
https://www.librarything.com/work/95127/covers/263590740 (7 custom covers available, missing cover# 15610555)

https://www.librarything.com/work/822799/covers/217465035 (6 custom covers available)
https://www.librarything.com/work/822799/covers/263590762 (5 custom covers available, missing cover# 15610552)

Well, never mind, now they've shown up. Weird though how some covers take longer than others to propagate through the system.