I've been having this problem since I started playing Arma 3 again a few weeks ago, and the annoyance of it has led me to post on this forum haha. The arma wiki has listed the problem codes failed_to_init_'xxx' or failed to write memory, and the possible causes for those codes vary from overheating, gpu drivers, steam overlay enabled, corrupt game files, corrupt system files, and HDD read errors. It's actually led me to install some software from NZXT that's great for monitoring cpu, gpu, ram, and system temperature.. which led me to rule out the GPU overheating since the bug would occur anywhere from 110-155 degrees.
I tried the old pre 1.66 fix of limiting memory by use of a launch parameter, but realized others pointed out that post 1.66 that parameter doesn't really apply anymore, along with enable HT (I did pick up some fps by setting my "cores" value to 4 via the launcher). However, so I could better anticipate the dreaded moment the 3fps bug kicks in, I decided to leave task manager opened on another monitor while I was playing so I could monitor Arma 3's memory usage.
What I noticed is that EVERY TIME the arma3.exe hits 3060-3070mb, the textures will tank, and the 3 fps sets in. I've also noticed that if I leave the game running, the memory usage value will creep down at a steady rate. While game play doesn't go back to normal, I've let it drop down to 2,970mb before closing the application. So, even though the game runs normally at anywhere below the magic 3060mb mark, once you hit that ceiling it appears only a re-launch of the game completely fixes the issue.
Thanks to the Devs for keeping us up to date with your progress. It's nice to know we aren't just trying to fix this ourselves
Mods Used:
CUP Vehicles
CUP Units
CUP Weapons
Enhanced Soundscape
Dyna Sound 2
CBA_A3
3den Enhanced
My Specs (2560x1440 resolution) Win 10 Pro x64
i7-7600k (@4.8GHz)
GTX 1080 (stock)
32gb ddr4
SSD system drive
2x 500gb WD HDD (arma directory)