Before I get into this, just know that I suspect Steam who is being lazy and directing me here. Could be them; could be Bohemia. Let me copy/paste what I said to them:
What a horrible problem. My desktop has been down for a few weeks, and when I got my hardware sorted out, I come back and try to play Arma 3. Steam seems to update every time I have to reboot my computer, as if the previous update didn't take.
Look, I have 180 days left before Steam stops working on this machine, but I didn't expect it to stop while my desktop has been down. Something is terribly wrong, and it takes out my monitor (or video card) whenever I start to move the Old Man player. No errors that you can see on your end, just turns off my monitor's HDMI connection and sits there banging on my hard drive/CPU until I turn my computer off and back on. Takes a while to even get my monitor to come back on after reboot.
I restarted the mission, thinking a file might've gotten corrupted, but it did the same thing the minute I entered Old Man and started moving him with my Xbox controller. I'm afraid to keep messing with this since it has caused my other monitor never to return. Dell replaced it. I also replaced the video card for this computer.
Stop messing with whatever controls this game, because I hate playing it on my laptop. It doesn't have a 34" monitor and I can't use my laptop while using this monitor at the same time. Not enough room by a long shot; my laptop can only sit in front of my 34" AW3421DW Dell monitor and covers it up.
What did Steam do to the client or game? I could try to play Call of Duty, but I don't like that game. Haven't played Ace Combat 7 in a long time, but I don't want to play that either. Especially if it's the Steam Client that is causing this issue. This is not the same issue as the other one, for Christ's sake. Only 1 issue at a time when I have 2 issues? COME ON!
So, what happened in the past 3 weeks while this computer was offline? I was on a roll with Arma 3 and am afraid to run this game on my desktop again.