I work end user support and I have a user that is claiming for months now that the computer randomly switches to high contrast mode. The screenshot he/she is sending appears to show the computer in high contrast mode, i.e. by using the Left Shift + Alt + Print Screen button to toggle high contrast mode. I have already trained him about these keys to ensure he is not somehow hitting them accidentally. We do not have personalization disabled so a user could potentially change the theme to high contrast. When I have he/she log in the colors randomly look fine. He claims it randomly occurs. I know there is no logging info for this in event viewer so it is difficult to determine if the user is doing it on purpose.

Is there anything other than using the personalization -> theme in settings or using the Left shift + Alt + Print Screen that would randomly turn high contrast mode on?

I have already disabled the ease of access center from appearing in control panel and also disabled it from opening.