Hey, have you tried making an expert world and trying to play on it for a while? Sure, might not be as hard as master mode but here's what I know:
A lot of people are talking about their master/journey mode world getting deleted, but not expert/normal worlds.
Coincidence? So anyways when I had a bunch of normal/expert worlds they didn't get deleted, as well as a few master/journey worlds (one journey world did get deleted however), but when I tried to create a new walkthrough master mode world and reloaded the game, it disappeared. Try that, if it doesn't work, reply to me.