Comment 12 for bug 1726548

This bug affects me as well.

I have only experienced the problem with Firefox and when...
--- closing my laptop lid and later opening it.

I have NOT experienced the issue when...
--- leaving the lid open and commanding the laptop to sleep.

I tried changing my resolution and scaling but the issue remains in all scenarios below:
  Resolution 3200x1800 (native resolution and my typical resolution)
    Scaling 100%
      Gnome Tweaks > Fonts > Scaling Factor 1.50
      Gnome Tweaks > Fonts > Scaling Factor 1.00 (default)
  Resolution 2880x1620
  Resolution 2560x1440

Dell XPS 13 9360
Ubuntu 18.04