You're at a point where temps will certainly come into play, so those need to be monitored either with RealTemp, CPUID Hardware Monitor, or the like.
Are you saying you get the whea errors when cpu is under load all the way up to the 1.395v? And then without any load other than booting into windows, you get an instant whea error at 1.4v? What are you using to load the cpu? Prime95, IBT, or ?
What do you have for cooling, and what are you using for voltage, fixed or offset?
Depending on what your bios/uefi options are, there are settings that could perhaps aid you in gaining stability. There's the Internal PLL Overvoltage setting, CPU PLL voltage adjustment options, etc. However, those are things I've never had to mess with as I have a crap overclocker of a chip. I'd have to direct you towards other members wisdom on these matters who have first hand experience. Definitely check/search threads for those running in the 5ghz realm, you may get some ideas. People will want to know your specs though, like board, cooling setup, whether using offset or fixed voltage, what your temps are, etc.