18.04 purple screen after sleep

I'm not sure if this is the same or related to bugs 1767893 or 1775045.

It seems like this happens after 5 minutes of inactivity when the screen goes to sleep. I had the lock screen turned off. In 16.04, I haven't had to type in my password after inactivity for years (I'm the only one using this computer). So now after this going to sleep or whatever, the screen turns purple, or maybe goes to the beaver picture. If I swipe up the touchpad, it removes the beaver, and leaves a rather dead purple screen. I click on the launcher icons on the left column, and they are unresponsive. I click on the lower left apps button on the screen or whatever that 3 x 3 grid of white dots is, and nothing. Some kind of swiping on the touch pad makes some icons sort of flicker across the screen in a diagonal, and quickly disappear.

Then I clicked on the little down arrow in the top right corner of the screen that usually leads to the settings options with the 3 circles: tools/settings, lock, and power button. But now they don't show, just a pause button in their place. I think I clicked the pause button and it powered down the computer. The hardware power button on the keyboard of the laptop turned off. I pressed it and then up came a login screen, quickly, no boot process, and I typed in my password, and then normalcy resumed.

Update 1: The purple screen and disappearance of the settings button and Activities tab has stopped. I'll wait a few days to see if these things happen again and if not, I'll try to initiate deleting or closing this bug (as spontaneously fixed without my doing anything). Maybe this happened because the computer was left in a state of limbo as I was manually merging and cleaning up the remaining dpkg-old and dpkg-dist files after the system upgrade to 18.04.

Latest update: The purple screen happened again although I'm not sure it was after a sleep. Then I did a regular restart and it seems fixed (until the next time it happens).