Comment 1 for bug 1503758

The workaround on https://code.launchpad.net/~hui.wang/unity-settings-daemon/unity-settings-daemon-master-touchscreen-fix/+merge/293704 seems to be to workaround the segfault there

in that the description is

"on a Lenovo laptop with the LG LCD panel and the LG touchscreen, when we change the display resolution, the LG touchscreen will be temporarily disconnected from USB host bus for about 0.2 seconds, then will be reconnected to the USB host bus. If we let the system call do_touchscreen_mapping() before the reconnectting, the u-s-d will crash."

so it seems likely that u-s-d gets confused by the screen being removed while configured, maybe some callback not being disconnected when they should...