humantoz... If you have access to a linux box you may want to try and format and partition the WD drive under Linux as i have had issues with some WD's that appear ok in Winblows but acts weird under Linux... LibreELEC is actually Linux and Windows isn't exactly the same at partition or low level.
I know the WD's will work as i have over a dozen 4terabyte wd drives in my network but usually if i buy a used drive from someone that had it on Windows i have issues with them on my devices... Usually running Linux fdisk at cli or use gparted will partition and format getting rid of the errors.
If you've got no Linux box just use one of the Live Distro's on a usb stick on your pc to just boot to a live non-installed version of Linux and use gparted or fdisk within that environment to repartition the drive.d
Sounds like when hooking up the wd on a running system LE is able to find the drive and mount it ok but when booting up theres something in the WD's partitioning that LE don't like resulting in the hangs...
Not sure if thats the issue but based on trying to use Windows formatted drives in a Linux box thats giving me greif thats were i would start...