On my wife's PS4, we always play Minecraft Dungeons under my local account (that is, I start the game). Twice now, I started the game and my character was there. Our two kids's characters were there. But my wife's character was gone. And, if my wife starts the game, there's her character! Of course the other characters are not under her account, so we still can't play together.

The first time, her character magically appeared again under my account and we were able to play together for a few weeks. Maybe that will happen again this time.

This is surprising: characters should not sashay from one account to another.

The only theory we have is that my wife often plays Skyrim under her account. Perhaps we left Minecraft Dungeons running under my account, then she logged in under her account, stopped Minecraft Dungeons, and started Skyrim. And when she did this her character somehow moved from one account to the other.

FWIW, we always play locally. Never online.