Reproduce:
* lock screen
* close laptop lid
= system goes to sleep
* open lid
> enter password to unlock
= screen blanks for a glimpse, goes back to login screen
> enter password to unlock
= screen blanks for a glimpse, goes back to login screen
eventually the session is unlocked then, sometimes I've to login again
Ubuntu Studio 18.04.1 LTS
xfce4 4.12
xfce4-power-manager 1.6.1-0ubuntu1
Reproduce:
* lock screen
* close laptop lid
= system goes to sleep
* open lid
> enter password to unlock
= screen blanks for a glimpse, goes back to login screen
> enter password to unlock
= screen blanks for a glimpse, goes back to login screen
eventually the session is unlocked then, sometimes I've to login again
Ubuntu Studio 18.04.1 LTS
xfce4 4.12
xfce4-power-manager 1.6.1-0ubuntu1