I've been running 17.04 for a while now, and other versions before that. A couple of days ago, I tried to install 18.04 (a new install, not an upgrade). I selected to erase and encrypt the drive. After the install finishes (apparently without error), and reboots, it reports
Failed to connect to lvmetad. Falling back to device scanning.
and repeats this error several times before dropping me into the initramfs shell. It never asks for the encryption passphrase.
On a whim, I tried installing LVM without encryption. That didn't work either, it seems to lock up solid before even beginning to print boot messages.
This is on a ThinkPad W530.
sha256sum yourimage.iso
to your question? – pim May 01 '18 at 11:03