I have experienced this error multiple times and can not fine the root of the problem. Have been able to duplicate problem on vanilla and modded Arma 3. Occurs occasionally and after long periods of gameplay. They're no signs of the error prior to it's occurrence and it persists until the game is restarted. The LOD of the textures will suddenly drop along with an fps drop to 3-5 FPS. Have checked thermal readings on CPU at the time of event, no temperatures exceed 40 C which is well within safe for my CPU
Video of Error:
https://www.youtube.com/watch?v=37SmotelH-4&feature=youtu.be