Watch your vcore when you run a stress test.
If the voltage is relatively steady and it crashes with just +1 on the multiplier, RMA the CPU.
(No voltage will be 100% steady, but it should settle into a very small "range" on each test.)
Oh, and let us know what vcore you are seeing under load.
It keeps like 1.3V there, but the thing is that I had the CPU for about a year now.