Upon logging in, I found that all entities had been deleted (villagers, minecarts, animals). I had dozens of farm animals in fenced enclosures. All gone. I had dozens of pet dogs and cats and birds. All gone. I was near a village with dozens of villagers. All gone. I had about a dozen librarian villagers in another location for trading. All gone. All of the minecarts that were on any of my rail systems: gone.

This is at least the second or third time this has happened (I think even before the 1.18 update), but it was more noticeable now that I had a well established farm. Now, it's undone weeks of work.

Update: I replaced all of the minecarts and logged out for a couple minutes to write up this issue. Upon logging back in, they're gone again. I guess I just can't play anymore.