Toshiba laptop screen randomly flickers wildly

Out of nowhere, my Toshiba Tecra R950 laptop has recently started wildly flickering and flashing vertical lines at regular intervals.

Strangely though, the flickering happens in some situations and not in others. For example, when I hit CTRL+ALT+DELETE the blue menu screen comes on and the flickering stops. Also when I expand the task manager to full screen, there is no flickering. The flickering also tends to happen much more while on certain web pages and application than on others. For example, when Gmail is open in the browser, it flickers a lot. But when on Google.com, it doesn't. For this reason, I am quite confident that this is not a hardware issue.

Does anyone have any ideas what could be causing this and how to fix it? Please see a video demonstration here

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Solution 1:

After spending a few hours uninstalling things, stopping services, rolling back to restore points etc... I found the culprit (partially)

The cause of the wild flickering was Night Light mode. I had enabled it around the time that the flickering started. This doesn't completely solve the issue and there must be another perpetrator since there is still an occasional flicker. But turning off Night Light mode alleviated the bulk of this issue!

To turn it off, type "Night Light" in the Start Menu, and then click "Turn off now" in the window.

I am still looking for the other culprit(s) and/or an explanation of why this happened