I have recently found that after upgrading to GNOME 3.20 on Ubuntu GNOME 16.04 that after a suspend often the time and date are either both missing, or the date is showing but is like a shadow itself (because it has the shadow like edges but is solid though sort of misty, so I'm going to assume that the shadow stayed but the actual proper text on top disappeared), or a combination between this (though not always a combination) and some of the numbers showing (sometimes with a strange shadow like underline for part of the time) for part of the time, so the seconds might show while the last digit is between 6 and 9 or something similar. But on this occasion it was all just missing, though pulling the shield up and down sometimes alters which one of these occurrences is present.
Upon pulling up the shield I noticed that all the buttons had their text removed, and when typing in my password, the characters were invisible too. After logging in (and the spinning animation thing for logging in was missing too) I found that all text was missing from all of my applications seemingly almost everywhere in my system at least, individual applications seemed fine with their own text, but everything related to gnome-shell seemed to be lacking text. As you can see here (the big black box over Firefox was something I added to the picture):
No_Text.png
No_Text_AO.png
The only way seemingly to correct this problem is to either restart gnome-shell (ALT+F2 and then 'r') or the machine. And just to add, all text that I type into system areas is missing (so not in Firefox, but anywhere else). This strange occurrence has happened at least 3 times now since I upgraded to 3.20 on this machine.
Though this may not be related, I thought I would mention it, after the upgrade to GNOME 3.20 was complete, all characters became little white hollow boxes until I restarted gnome-shell.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: gnome-shell 3.20.2-1ubuntu1~xenial1 [origin: LP-PPA-gnome3-team-gnome3-staging]
ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
Uname: Linux 4.4.0-22-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: GNOME
Date: Tue May 31 22:48:48 2016
DisplayManager: gdm3
InstallationDate: Installed on 2016-05-15 (16 days ago)
InstallationMedia: Ubuntu-GNOME 15.10 "Wily Werewolf" - Release amd64 (20151021)
SourcePackage: gnome-shell
UpgradeStatus: Upgraded to xenial on 2016-05-28 (3 days ago)
These strange occurrences happen rather often, and in the latest of one of these when I logged back in again everything had gone mad, the selected window was madly flashing (going between the focused and unfocused state very quickly even though I wasn't doing anything that should cause this, in fact, most of the time I wasn't doing anything at all) and so text from half of the date and time at the top, and the Activities Overview text, when I finally managed to close the window, the flashing stopped on that side of the screen and then the window which was behind the other one grabbed another part of my screen and started having the same affect on it.
I wanted to shutdown my machine, but when I opened the pull-down menu with the shutdown button I noticed that all text had gone, it only returned, though briefly, when I went over it with my cursor.
And as this is all happening rather regularity and getting worse, my machine is becoming harder and harder to use, I'm having to restart gnome-shell all the time.