about OC tuner... maybe you're using an outdated version but with me it clearly says "NB voltage" which reads the vCPU-NB i set in bios, and "mGPU voltage" which reads 1.146 V since i left that on Auto in BIOS. Now, you're saying you bumped mGPU from 1.4 to 1.5 V, but couldn't it be that the default value is 1.15 V ? perhaps you're overvolting this thing too much right now, and perhaps setting 1.3 V for mGPU in BIOS should do the trick as well?