Boot Device LED on then off ??

[RyansPrivates]

Hello All, 
Having an issue that I encountered a few days ago when installing new fans.

Issue: Computer boots to windows login, then shuts off. Second boot stays on fine.
The Boot Device LED is on during 1st failure, and off during second. Doesn't matter how many times or how long i wait to boot computer, EVERY OTHER boot has Boot Device LED on and shuts down.

This began when I bough new RGB 120mm fans for my case. They worked fine for a few days. I realized I need to move the air flow and switched them up a little. All was well, until the switch. 
I noticed the RGB lights would dim at Start Up and then go back to Full Power and then the PC would shut off. 
I disassembled my PC, everything, re-coated CPU with Thermal, cable management, fans, changed Memory slots from A1-B1, to A2-B2, and inspected and re-set everything.
I also changed RGB fans from Chasis Fan connectors to straight to PSU, which solved the low power mode on them, and no longer dim.

Everything seems to be running fine when it works, and used 'Hard Disk Sentinel' to inspect drives. everything is fine.
But have no idea why the Boot Device LED is on every other boot.

PC SPECS:

MOBO: ASUS Z170E
CPU: i7-6700k
CPU Cooler: Corsair Hydro Water 

Memory: 2x8 Corsair Vengeance LPX
Bootable Drive: Intel NVMe 750 400GB
Storage Drives: 2x Western Digital Blues 1TB & 2TB
GPU: ASUS 1060 6GB

Thanks in Advanced people!