Maps and item frames disappeared after updating to newest snapshot.  This happened a few snapshots ago too but they came back with a later update.  It's back again in 19w08a.  Possibly of interest...When loading the game, if "show subtitles" is on, an item frame will be placed then is removed.  The sound of it being placed can be heard as well as the subtitle.    When I went into my map room all the maps and frames were on the floor and all frames and items in frames are gone throughout my build.  I was unable to put the frames back on the same wall so I built a new map wall.  After exploring I came back and all frames and maps were again gone.  I was again unable to place frames back on the wall in the same place.  Maps and frames were not on the floor this time.   I apologize if this has been reported.  I searched but found nothing.    Cheers!