Monitor Loses Signal When Running Games at Native Resolution, Computer Still Runs

[WhatsGoingOn]

I built my own PC in the summer. In the past couple of weeks or so I've been having a problem where my monitor turns off and the PC locks up, meaning I have to restart it using the button on the front of my tower. The sound stays on for a few seconds afterwards before cutting out as well. It started whilst playing Gears of War 4. Strangely enough if I put the resolution down very low and change the aspect ratio to non-widescreen it doesn't lock up. This doesn't occur when watching videos or doing anything else on my PC - it's only when I start gaming, but does occasionally happen when logging in or as soon as I start the game.

The event logs show errors but they're all to do with having to restart the computer using the button and not about the crash itself. My specs:

EVGA GTX 960
Core i3 6100
Western Digital Caviar Blue HDD
Kingston HyperX Fury Ram 2133 mHz DDR4 8GB
Asus H110M-A
Seasonic 620W 80+ Bronze Certified PSU
Apple Cinema Display 20" 1680x1050
Windows 10 Pro 64-Bit

So far I've tried:

- Using chkdsk. No problems found.
- Verified HDD contents using cmd
- Reinstalling Windows 10
- Updating GPU driver, rolling back GPU driver, uninstalling GPU driver
- Checked if GPU fans work with MSI Afterburner. Monitored temperatures in game - normal, around 60 before crashing. Approx 40 idle.
- Changing power supply socket
- Reinstalling all games
- Running games windowed
- System restore (didn't work because of a WindowsApps issue)
- Checked motherboard BIOS. Could update but it's only to support new technologies - it doesn't include bug fixes

It seems as if the GPU locks up when running games at native resolution and aspect ratio. For example when I try playing Chivalry it works perfectly because it's run in letterbox mode. I also accidentally knocked my tower recently with my foot and it shut off - could there be loose internal connections?

Any ideas? Thanks so much in advance.

 

[mdd1963]

If simply bumping it with a stray/errant foot causes it to reset/crash, something is not quite right; shut it down, remove power cable from PSU, and reseat all internal connections, as well as reseating the memory sticks and the GPU, power connector harness to mainboard, along with GPU's supplemental power connection. Then try again.

 

[Vz97]

Have you fixed the problem yet mate..??

 

[WhatsGoingOn]

Have you fixed the problem yet mate..??

I can't tell to be honest with you. Opened the case, removed a bit of dust and ensured everything was secure.. it's stopped shutting off but not sure whether it's just coincidental! Will make the first response the "answer" in the meantime though.