Comment 7 for bug 1408263

I built touch-debug packages of unity8 to get as much output as possible for this.

Interesting data point: playing music seems to trigger this more often - suspicion is not allowing the device to fully suspend increases the chance to get this bug.

To get the debug-enabled unity8:

$ wget http://people.canonical.com/~msawicz/unity8/touch-debug/repo-key.pub
$ gpg --homedir /dev/null --with-fingerprint repo-key.pub
# verify fingerprint: C09A 0EA9 555F 5A80 D53B EE1F 47EA 8F76 B005 9747
$ sudo apt-key add repo-key.pub
$ sudo add-apt-repository "deb http://people.canonical.com/~msawicz/unity8/touch-debug/ /"
$ sudo apt update
$ sudo apt install unity8 unity8-common unity8-private
$ sudo reboot

if you reproduce the issue, grab unity8.log and unity8-dash.log from ~/.cache/upstart/ and upload it somewhere.