If that’s during the shutdown, it means that a task has not been terminated properly prior to shutdown. E.g. an external drive or an encrypted partition has been mounted, especially when there is an open file on that drive/partition. You might have something running such as VeraCrypt, which prefers to unmount its own drives. As an experiment, make sure all files and all applications are closed before a shutdown. If it’s still a problem use htop to see what else is running under user ID 1000. Look carefully to see if anything is running that shouldn’t be, get the process ID and kill that task. Then reboot.