Hello,
I just found this thread today.
I have been running into the same problems in my S4M / i7-8700 / ZOTAC 1080 mini / HDPLEX 400 build as well.
I have tested with 2 different external power bricks (Dell 'genuine' LA330PM160, though not purchased from Dell. HP Omen X 330W bought from HP)
With a standard ATX 550W, I don't get any power resets at all.
With the HDPLEX 400 + HP Omen X 330W, I get power resets even with the Zotac 1080 mini removed.
With the Zotac 1080 mini still removed, I can get a stable system if I change the default 65W Turbo Max / 82.5 Turbo Short Max down to 60W Turbo Max (and 60W Turbo Short Max)
Stability testing is done via a quick 'Bench' run in Intel Extreme Tuning Utility
If I add the Zotac 1080 mini back into the mix, I can't get a stable system even if I lower the CPU power limit down to 20W for both Turbo Max and Turbo Short Max.
I am hoping to test with another HDPLEX 400 unit soon.
