Try testing the OC settings sticking by going just 1Mhz over stock speeds (gpu or vram or both, wherever you are having the issue) and seeing if that sticks beyond the time where your other OC normally reverts.
Let us know how it goes.
Ok I had an overclock of 30mhz on core and 50mhz on memory. but i also undervolted so there wouldnt be temp issues., and i read online that undervolting polaris card is better. Maybe i undervolted by too much (-25mV) but now i am at around -10mV and still maintaining that overclock. Did a firestrike bench and doesnt seem to be any issues and havent had any reverting back to default clocks so hopefully that fixed it.
Hopefully this helps anyone else.