Thank you for contacting Intel Support,
I can see that you are having issues with an Intel® NUC7i3BNH since it is freezing during each period of inactivity, I apologize for any inconveniences this may be causing.
Regarding the problem, I was researching to find a solution for you, however I came across an article which shows the supported Operating Systems for the different Nuc units, please refer to the following link:
As you can see, the only Operating System supported by the NUC7i3BNH is Windows 10 64-bit. I apologize for the problem, however the Operating System showing the problem is not supported. If you can, please try to install Windows 10 and test the system to see if it still freezes or not.
If you have to use Ubuntu then I would recommend you to direct the question to the Ubuntu/Linux forums so that they can attempt to help you with the problem.
It appears that Crucial ValueSelect SO-DDR4 4GB 2133MHz (1x, 4GB, DDR4-2133, SO-DIMM 260 pin, CMSO4GX4M1A2133C15) works fine if and only if one and only one SO-DIMM is installed. When you install two SO-DIMMS, the unit freezes after 4-7 hours consistently. With one, it has not gone down in 2 days and counting.
Thank you for your response,
I understand that you mention only one RAM at a time fixes the issue as it is not going down so far. Nevertheless I would like you to give it a try with a different memory module if possible. Trying a different pair and see if it shows the same results, of course if it is not possible then I understand.
Here is a list of the tested memory modules and peripherals that are known to work with your NUC7i3BNH:
If possible try a pair of modules from the ones listed in the tested peripherals. If this shows the same symptoms then let us know please.