In my Arma experience, this is usually caused from Arma 3's proprietary memory allocation it tries to foist on your computer. Go into your Arma 3 folder, find the DLL folder, and within it, you'll see several files with malloc designations. Delete these, and naturally, reboot your Arma. This will allow your computer to use its already tried and true method of memory allocation, instead of Arma 3's, which causes more issues than it solves.
Give it a shot. It'll cause no complications, and the files can be re-downloaded by verifying your game cache.