I also have this issue in windows 10 realms. seed 690589143. I can't get coordinates but if I make a map at spawn and zoom it all the way out, when I go just north of that map to make another map is when it happens. It happened in a couple different areas not far north of the first map.
Using a blank map caused it to generate a blank map for a second, then the realm crashed. When I came back, the map was no longer in my inventory.
I had a recent issue where my 2 tamed horses (one saddled with armor, one unsaddled) disappeared after game crashed while I was in another chunk, and their leads vanished, but the fencepost with the tied-up portion of the lead was still there. If I try to grab the lead off the fence post, the lead does not drop itself.