Don't you have ubuntu tweak installed? If so, don't you have set under Tweaks > Session indicator "Disable lock screen?" If unsetting it corrects your problem, could you set this to invalid? Otherwise, set it to confirmed.
Don't you have ubuntu tweak installed? If so, don't you have set under Tweaks > Session indicator "Disable lock screen?" If unsetting it corrects your problem, could you set this to invalid? Otherwise, set it to confirmed.