Ok, started a 3rd world and same thing happens. Day 4 around 22hours, quit game have dinner, come back to original spawn point and level 1. Go back to my base and everything is still there but "jammed", my bike says it belongs to another player. It's treating me as if I were an new player joining the world. It doesn't recognize me as the original player. This time I'm going to continue to play and see if it happens again. I'll use the creative menu to return my lost gear. Nothing to be done about the skill points/levels lost but to redo them.