Playing on Xbox Series X splitscreen. When 2nd player signed in after latest update (April 6th 21) all items were lost and start point changed to position when previously updated a month or so ago after nearly playing everyday since then.
We tried loading previous days backup and xbox restart, then player 2 signing in but made no difference.

We had similar issue with previous update, player 2 signing in losing everything and starting at original spawn point. We worked around this by loading back up and player 2 signing in first putting everything in a chest, saving signing out. player 1 starts then player 2 joins and it's as if it's their 1st time playing with on screen tips and had to go and get everything back.