I had a bunch (maybe 20 or so) maps up on a wall in my central base to make an overview of the areas I'd settled. Having set up a new base, I was going to add a series of maps reaching over to it, just after downloading 13w38c. However, when I looked at the first new map, it was blank at had a location marker in the center of the far-left boundary--and all the maps in my map room, as well as their item frames, had not only gone blank but ceased to exist. I tried hitting the wall to see if they'd just gone invisible, but it made the stone-hitting sound as though nothing was there. I'm a bit upset at the loss of the map room, but mostly totally mystified...