Why MSI Afterburner apply random voltage.

[Winterlight]

Any idea how fix this random voltage jumps? I set curve 2730 Mhz at 975mV but problem that voltage randomly jumps. I did stress test and it was fine until midle than voltage randomlly jump to 990mV while clock still keep same 2730 Mhz As well tested with 900mV at 2550 Mhz and no matter what I do it never run at 900mV always jump to 910mV same with 950mV-970mV it never run at this values always jump to higher.