A few ideas.

1. Be sure the monitor is on the GPU.
2. No go? Remove the 1060 GPU and use onboard graphics.
3. No go? Make the PC as small as possible. No case, just motherboard and min parts on cardboard and if that fails you are looking at the failed part or parts. It won't tell you if there is some failing PSU, CPU, motherboard but it can get you to the least number of parts to RMA.