In the UEFI bios you should go into the voltage or temperature monitor section to see if the voltage is matching 1.50v or more for specifically the RAM. If it is, don't bother with changing it yet. Since it's an X79 board it has XMP profile reader built-in to the Asus tweak section that will read the SPD information on that RAM and set timings accordingly.
Another thing you can do is lower the RAM speed to 1333mhz and see if the crashes are gone then. This is also in the Asus tweak section of the UEFI BIOS.
You also might want to save your OC in an OC profile and see if you need a BIOS upgrade.
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