I have a duplicated item in my hands and can't continue
Sometimes when spam-clicking or simultaneously clicking an item, the item can get duplicated in your hands. This may only be a visual bug that could disappear by spam-stealing the item from each other's hands. If this did not work, you could try to “Start a new Journey” in the lobby and manually select the checkpoint you left off at or a checkpoint before that.
A bug is preventing me from continuing the game
Select “Start new journey” in the main menu and manually select the checkpoint where you left off or a checkpoint before, and try again. Make sure you have a strong and stable internet connection as well, as network instabilities can cause desyncing issues with the games.
You could try to verify your integrity files to repair any damaged game files as well.