After installing EE v5.1.8 on a dell mini 9 it no longer boots into Windows. The initial install was successful and it looked to encrypt just fine. On the next reboot you're prompted with the EE login but once you click ok, you get the mouse cursor and nothing else. It is completely hung.
On our Dell Eseries we had to turn on a feature in the fileset. Not sure if this would fix your problem too or not but its worth a try. Their is a feature in the fileset option that say "Detect number of Sides of the OS" Turn this on in a test container, build the fileset. Then encrypt the computer.