What BIOS version are you on at the time of writing? In fact considering that this is a troubleshooting thread, you're advised to include your specs to your build. Please list them like so:
CPU + CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
include the age of the PSU apart from it's make and model and it's wattage. As for your EZ tune, see if there were any updated versions listed on Asus's support page for your motherboard. The best course of action when overclocking is not to rely on an app or the OS, instead you should manually go into BIOS and tweak the system.
Speaking of which, might want to see what sort of voltages your processor is/was at. High(or low) voltages can cause instability.