Seems to be the same bug as https://bugs.launchpad.net/ubuntu/+source/light-locker-settings/+bug/1574544
This post report also a similar problem : https://bugs.launchpad.net/ubuntu/+source/light-locker-settings/+bug/1602338
I lately saw that the bug is already fixed so may be you can close both this and #1602338 issues.
Seems to be the same bug as https:/ /bugs.launchpad .net/ubuntu/ +source/ light-locker- settings/ +bug/1574544
This post report also a similar problem : https:/ /bugs.launchpad .net/ubuntu/ +source/ light-locker- settings/ +bug/1602338
I lately saw that the bug is already fixed so may be you can close both this and #1602338
issues.