Windows 10: One monitor randomly becomes disabled

The computer:
An all-in-one desktop PC with an external graphics adapter to add a second monitor, running Windows 10 (free upgrade from 7).

The problem:
Lately the primary monitor has been spontaneously becoming disabled with no prompting from the user or discernible pattern. The display settings are "Extend the display," with monitor 1 as the all-in-one and monitor 2 as the independent monitor. Repeatedly now, the settings have changed themselves to monitor 2 as the only display, with monitor 1 disabled.

It is easy to change back, but this becomes aggravating after it happens again and again!

Attempted solutions:
I'm at a loss. I've tried googling things like "windows 10 monitor becomes disabled," but no matter how I vary it the results bring up instances of Windows 10 itself becoming disabled. I can't find anything wrong with the settings, but most of my experience is with Windows XP through 7, with limited work on 8 and no work prior to this on 10.

Is this a rare problem? Can anyone please suggest a solution, cause, or better keywords for me to use?

Thank you and let me know of any more specs that you want me to post.

:)

 

How to Disable Split Screen Function

I have two monitors, but when I drag a window from one screen to the other it gets stuck initially at the edge and tries to become split screen. Because I have two monitors this tool is redundant and gets in the way of quick browsing. Is there any way
of disabling it?

 

Dual monitor in Windows 10

The cursor glitches problem mentioned in another post is exacerbated with dual monitors. The cursor randomly jumps from one monitor to another making the second monitor unusable.

 

I run triple displays on my desktop PC. And dual on my laptop via a USB 3 potable monitor. I haven't had them switch on their own. Especially to external only. Pressing the Windows key *Start on the keyboard and the P key will open the selection menu. Is that maybe happening by accident with a keyboard script or something? Grasping at straws I know, but its all I have at the moment. Unless its an application switching to projector mode?

 

Thanks! We've never used this computer specifically with a projector, but it's entirely possible the user (my boss) is hitting Win+P+P by accident. Sorry, I should have realized that possibility! The corollary question is why this has never been a problem on any other computers, since he's been using various multi-displays for years. I'll check with him and return to this thread when I figure out if he's changed keyboard configurations or injured a finger or something.

 

It was just a wield guess to be honest. A menu bar pops opens down the right side when you do it, and should be visible. Unless he's like me, type away, then look up and do spell corrections, lol. I use shortcuts to switch to "PC only" when gaming, and then back to Extend when I'm done gaming. Even with those the menu bar pops up for a second on screen.

I don't know about all in ones, but laptops have a special function key to switch to projector mode. It would be fn key and an F key. All in ones are close to being a laptop or tablet, just no battery.

 

I already checked his computer and the side menu absolutely pops up; pressing the Windows key and then P twice will switch to external display only. But he isn't in today, so I couldn't talk to him about it. He doesn't have any reason I know of to change the display settings, and when he showed me that he knows how to change it back to extend he used the "right click on the desktop, select Personalize..." method, so I don't think he knows the hotkeys. The keyboard that he's using isn't the one that came with the computer, and has no special keys related to the display.