Screen Freezes Up - including when running Memtest86

[Tex]

New Intel NUC10i7FNH in March. Transitioned info over to NUC and began having random screen freezes, requiring a hard reboot. Have spent six weeks running diagnostics, making sure correct drivers installed and not updated automatically by windows and removing one peripheral at a time - only to see freezes continue. Freeze takes a few forms - white, black or colored screen, but most commonly just freezes with whatever is on the screen at the time and the mouse and keyboard do not function. Unplugging/replugging either do not work. No identifying info in Win 10 Event Viewer or Reliability Monitor to help diagnose. Intel is very slow to respond online. Freezes multiple times a day when I had thunderbolt connecting to 2nd monitor (thunderbolt to DVI cable), but absent that it freezes daily, a couple times a day, or maybe every 4 or 5 days.

NUC has two Crucial 8gb 2666 memory sticks, Samsung 970 Evo SSD M2, Samsung 860 Evo SSD (sata). Besides monitor (HDMI to DVI cable), I now only have wired Logitech keyboard and Wireless M570 Logitech trackball using Unifying Receiver (firmware updated). Still get random freezes. (Started with hub, 2nd monitor using thunderbolt, printer, diff keyboard and mouse even).

Have run Intel CPU diagnostics. Have run Memtest86 twice, each time about six hours to complete, no errors. Last night I ran Memtest86 again and it froze 28 minutes in, on test 10. Since booted direct from USB, this freeze eliminates Windows 10 64bit as a cause.

Memory? Motherboard? Suggestions for next step?

[Tex]

Since posting the above, I removed one memory stick. I did the windows 10 memory check, which reboots, and the computer froze 39% of the way through pass 1.

I then pulled that stick and put in the other. It successfully completed the windows 10 memory diagnostic. I started memtest86 and it froze 11 minutes into testing. Using the computer normally, I continue to get freezes, so the freeze was not limited to memtest86.

So never any memory errors reported, just computer freezes.

Since memtest86 boots from USB, does that eliminate windows as a cause? Does it eliminate my SSD M2 as a potential cause? Is it possible the freezes are the result of bad memory despite completing tests with no memory errors at times?

Or should I just tell Intel I want a new NUC under warranty?

I appreciate any help or insight.

[David (PassMark)]

Try running with just 1 RAM stick at a time.

But yes, bad RAM can cause software to fail / freeze. Including Memtest86, if the bad memory address is at a location being used by MemTest86 for it's executing code.

Yes, it pretty much rules out Windows and the M2 and SATA HDD as being at fault.

[Tex]

Thanks. I already have run with one stick at a time and have freezes with each as detailed above (one stick froze during Win 10 memory diagnostic), the other froze during memtest86 and in regular use.

Buy new memory? Return the NUC?

[David (PassMark)]

If it was new and came with the RAM pre-installed, then yes I would return it.

[Tex]

It was new, but it was not a built system, so I bought the memory.

I decided to buy a stick of memory. When it arrives will try it and if freezes continue ask Intel to give me a refund under warranty and move on to a different computer altogether.