I have multiple hard drives hooked up to my computer (2tb WD portable, 2tb segate portable, 4tb Toshiba 2 tb Toshiba and two 6tb WD mybooks ).
The two Mybooks will randomly disconnect at anytime when their idle or when im using them. I have disabled auto off in both the power settings and the wd tools.
it only seems to happen when i have them hooked up to my desktop (running windows 10) they work perfectly fine on my laptop (running Kodibuntu)