It isn't core fluctuation, rather a power issue that i also started to have with the first crimson. Just try it and force even the stock clocks on msi afterburner, and you will definitely pass the 12000 points on the graphics score. Don't even touch the powerlimit, voltage offset or anything. Just put the same core and memory clocks as the factory oc and apply it. You won't lose anything. It is the same issue i had and already pointed it out on an earlier thread of a crimson driver. As for why he is going passt the 13000 on the factory clock, maybe his tessellation is somehow connected.