Application r5apex.exe has been blocked from accessing Graphics hardware

Product: Apex Legends
Platform:PC
Please specify your platform model. PC
AMD or Nvidia Model Number nVidia Geforce GTX 1080ti Aorus Xtreme edition
Enter RAM memory size in GB 16
What is your gamertag/PSN ID/EA Account name? DELTASABRE69
Please provide your squad mates' gamertag/PSN ID/EA Account name if possible.
Which Legend were you playing (if applicable)? Lifeline
Which Legends were your squad mates using (if applicable)?
Where did the issue occur? In a match
Which part of the map or menu were you in? If you don't remember the exact name, please describe the area or what you were trying to do in the menu. Happends all over the map
What were you doing when the issue occurred? E.g. respawning a squad mate at a beacon, using an ability, a squad mate left the game. Can happen when just running, or looting, or shooting, or dropping... any time
Did your squad mates also experience the issue? No
How many matches had you played in a row before the issue occurred? 1-2
When did this happen? (dd.mm.yy hh:mm) 20/02/2019 02:45 UK time. But happens multiple times a session
How often does the bug occur? Every time (100%)
How severe is your issue? Major impacts to gameplay
What happens when the bug occurs? Screen freezes. I have to crash to desktop and kill the process.
What should be happening instead? Games should not freeze
Steps: How can we find the bug ourselves? Unsure. happy to provide any diagnosti

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Specs:

CPU: i7 7700k @ 4.8

GPU: Aorus 1080ti Xtreme

RAM: Corsair Dominator Platinum 16GB 3866

Fully custom water loop and temps are all low (max 55c)

I can play for maximum of 1 or 2 games before the screen freezes and I have to go to task manager to kill the process.

When running all latest drivers, near enough all settings on max with the exception of texture streaming set to high, when it crashes I get an error in the event log saying;

Display driver nvlddmkm stopped responding and has successfully recovered.

To try and fix this, I tried running the game as admin, running it in compatibility mode for Windows 7, same for easyanticheat. That didn't work.

I then tried adding the reg keys for TdrDelay setting it to 8. I still get the same freezing, but now I get a different error;

Application r5apex.exe has been blocked from accessing Graphics hardware

I then repeated the above two tests on older drivers, and I still have the same problem.

This is seriously annoying. I have a friend who has exactly the same setup, but with a 1070, and he doesn't have this problem.