Ive got a 1.5 TB WD black Edition drive, i've narrowed down my missing Textures to none other than fragmented files. if it takes too long to load, the client seems to just stop trying. I've fixed this by getting Auslogics Disk Defrag and performing the Defrag&Optimize files option.

(Auslogics is free and works wonders, its much better and faster than the ancient Sysinternals Disk Defrag windows uses.)