https://bugs.freedesktop.org/show_bug.cgi?id=110117
--- Comment #13 from Alexey Shindin freazav@gmail.com --- I can confirm this behavior at Ubuntu 18.04.2 LTS with Acer PH517-61 notebook.
The minor addition is that the issue concerns only the built-in display. In two display configuration after wake up the external display seems to be normal.