I tried to install 1.2.0-EPA2 on an usb stick. install image runs fine but it won't boot.
Please see Video http://download.rcs-networks.com/Vyos_install.mp4
I haved fixed it with booting again from the live iso mount the usb stick :
sudo mkdir /mnt/sdb1
sudo mount /dev/sdb1 /mnt/sdb1
sudo grub-install --force --removable --boot-directory=/mnt/sdb1/boot /dev/sdb
After this the system boots from USB. Same issue in Virtualbox