You may need to increase the voltage a tad to stabilize the OC out. Personally, I only OC my cards when I am benching or if I need to in a game, otherwise in any all 2D environments it really doesn't do you any good.
Try out MSI Afterburner to be able to adjust your gpu vcore. You will need to go into the "MSIAfterburner.cfg" file and change the following settings:
UnofficialOverclockingEULA = 0
UnofficialOverclockingMode = 0
UnofficialOverclockingEULA = I confirm that I am aware of unofficial overclocking limitations and fully understand that MSI will not provide me any support on it
Please bear in mind that by changing these settings and using the program you run the risk of damaging your card if you haphazardly OC it. You should always take your time and bump your freqs and voltages in small increments......and ALWAYS pay very close attention to your temps!
UnofficialOverclockingMode = 1
Further information concerning the program and how to use it can be found on most OC sites. Please research the program and become as familiar with how to use it safely before you begin using it.
Not to beat a dead horse, but use this program at your own risk......you have been warned.
Good luck and if you have any questions please feel free to ask.
The opinions expressed above do not represent those of Advanced Micro Devices or any of their affiliates.