You need to make sure the "Extra" voltage level(s) are applied as well. If 2D voltage is 1.05V, and 3D is 1.22V, there is no way you will get stable 3D clocks at 2D Volts. Check out the voltage tab, and set Voltage 1 and Voltage 2 to whatever the highest of the 2 of those is already set to.
They may be labeled Extra, 3D, thrtl, and 2D, depending upon your BIOS type. Leave Thrtl at default(if it's even an option), since this is what the card is supposed to step down to if it's overheating.
*Those voltages are listed as examples only. Use what your card has for default "Extra."
ASRock X99 WS i7-5930K @ 4.4GHz /2x GTX 970 @ 1.46GHz /4x4GB DDR4-2666
Phenom II X6 @ 3.7GHz /2x2GB DDR3-1680 /GTX 970 @ 1.40GHz
450-600K PPD @ ~850W