I recently purchased some of the Augsburg Fortress books. One of them came into my Library with the "Last Updated" column blank. Something seems amiss!

I did some stuff that caused the Library to refresh, and the problem went away.
I've seen similar glitches in the past with blank columns in the Library. Have never been able to come up with a consistently reproducible case, but just wanted to document that the bug is still lurking around there.