More a note to myself, but hopefully it will be helpful to others too! After updating to KUbuntu 16.04 a few months back, I had an issue where when I closed the lid to suspend the laptop, and then opened it again it presented both a gnome login/password screen and then a KDE5 password screen. When I used the button, or some other times when I suspended it only showed the KDE 5 Plasma unsuspend prompt. After some googling around I found a SO thread which pointed me in the right direction.
Going in to the
dconf-editor I deselected the
ubuntu-lock-on-suspend options and I’ve not had this issue ever since