You’re lucky that you can still access the disk. I got the same message on a My Book Essential aa soon as I enter the password. The operating system then goes into a loop and becomes unuseable. I’ve been in contact with WD support and have tried everything they suggested with no luck. They now agree that the disk is only useful as a paper weight.
After all the problems I’ve had with very high CPU and I/O usage and now this I know for sure I will never buy another WD product.