Comment 35 for bug 1646277

It sounds like the best approach is to bisect through the Ubuntu Xenial kernels. We need to identify the last kernel version that did not have the bug and the first that did. Can you test the following early Xenial kernel:

https://launchpad.net/~canonical-kernel-team/+archive/ubuntu/ppa/+build/9583414

Note, with this test kernel you need to install both the linux-image and linux-image-extra .deb packages.