Minecraft progress not saving!

This has happened to multiple people I know and, multiple times on my realm!  I save and exit the game YET when I reload it later on or the next day, my progress has not been saved.

This issue has affected:

• building progress
• Mining progress
• animal breeding (this has caused all sheep to disappear)
• items in Hotbar (items from Hotbar disappear and appear in random chests or disappear completely)
• achievements being lost

Many of my realm members have mentioned that large amounts of progress are not saved! This issue started a few months ago and has gotten worst now when mining tiles don't drop and slime spawning is out of control!