Without knowing anything about your exact footage, effects used, render settings etc. nobody can tell you much. This could even be merely a problem with e.g. using 32bpc mode and some effects not playing ball. Also check your GPU settings and graphics drivers. I smell a potential compatibility issue with your CS6 vs. the all too new card and you may need to tweak something.
Layers have Optical Flare and Element 3D. Render Setting is PNG Sequence no compression, working on 16bpc. I did switch it to 8bpc, same thing happens, When you mention GPU settings, I'm not sure what kind of setting can I mod on my MSI, I didn't touch voltages or OC the GPU. I got the GPU shows up in AE preference, so it recognizes the GTX 1070 and not using CPU rendering.
I tried turning off "Render Multi Frame Simultaneously" and this artifacts seems to go away. It takes a bit longer to render, still waiting but at least I'm not battling with the Re-rendering frames continuously.
Read something about Render Multi Frame Simultaneously, may be overflowing buffer of some sort with the GPU??? I don't know. Is this function not compatible with GTX 1070??
I could see multiprocessing, Element 3D, and that brand new GPU having issues, yes.