Xubuntu 16.04.2 ISO sometimes boot into isolinux and sometimes not when using a VM

[Marcelo Cerri]

When trying to install a VM using the Xubuntu 16.04.2 amd64 ISO, it boots randomly into isolinux and sometimes directly into ubiquity.

On the host:

$ cat /etc/os-release
NAME="Ubuntu"
VERSION="16.04.1 LTS (Xenial Xerus)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 16.04.1 LTS"
VERSION_ID="16.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
VERSION_CODENAME=xenial
UBUNTU_CODENAME=xenial

$ dpkg -l | grep libvirt
ii gir1.2-libvirt-glib-1.0:amd64 0.2.2-0.1ubuntu1 amd64 libvirt glib mainloop integration
ii libvirt-bin 1.3.1-1ubuntu10.6 amd64 programs for the libvirt library
ii libvirt-glib-1.0-0:amd64 0.2.2-0.1ubuntu1 amd64 libvirt glib mainloop integration
ii libvirt0:amd64 1.3.1-1ubuntu10.6 amd64 library for interfacing with different virtualization systems
ii python-libvirt 1.3.1-1ubuntu1 amd64 libvirt Python bindings
ii python3-libvirt 1.3.1-1ubuntu1 amd64 libvirt Python 3 bindings