^This^
It's a sign of instability. That's why we load test. If your temps are good and you have room for more v-core voltage, bump it up a notch and retest. (Or consider a LLC adjustment)
Keep an eye on voltage at both heavy and light loads. I had to adjust LLC from auto to "high" in order to stabilize the 4100 I OC'd at 4.4 Ghz.