i got this on video in 1.16.0.51: https://drive.google.com/drive/folders/1v7IuqCna2O6enG8eishW_h0W6RiYqiZC?usp=sharing, the videos are to big for this site tho.
1.16.0.51, the maps are still somewhat bugged, creating them will result in a 4/4 map, but copying a map will keep the correct size.
if it took more then 5 minutes to get back, the items probably despawned, this is a game mecanic
my base is fully above ground, but i guess every 5 seconds (it is a consistant interval) a random cave sound plays. even if i'm standing in broad daylight.