Shhpoons

If I run the system stability test on my system, and add the GPU, I get severe lag. Basically the screen appears to refresh every 1 or 2 seconds, and so the mouse jumps around the screen. It made clicking the Stop button pretty tricky. Anyway, I know its designed to push the GPU to its limits, but I haven't experienced lag like that when benchmarking in Heaven or 3DMark. All the benchmark scores in Heaven and 3DMark are pretty much on the money for my card, so I'm just wondering why I'm having issues here? My card is a Zotac GTX 1070 Mini (no OC). Or is this behavior expected when running the stress test?