I am sorry you are having this problem with the product but let me help you.
We strongly recommend users using direct connection (no adapters) so I would like to know if you have tested the NUC with direct connection to the monitor?
Check the tested peripherals here:
Can you also attach the dxdiag report here?
How to get it?
Dxdiag Report: Type dxdiag in Start Menu> open> Save> Attach using Advanced Editor Options.
Direct connection works fine without any issues. However there are some situation where VGA is only option. For me it`s projector. When I found that image is flickering on projector I tried to connect monitors too to determine if it`s projector or NUC issue. From everything I tried I found out that this has to be NUC (BIOS or graphics) issue because everything works fine on Mac, in Bootcamp too.
I purposely bought Bizlink adapter (MDPVGA) which si marked as supported and I have same issues as with Apple`s and chinese one.
DxDiag is attached.
DxDiag.txt.zip 14.3 K
If your NUC model was equipped with HDMI or DP, then you will need to use straight video cables, in other words, same end on both sides of the cable. Please bear in mind that, the usage of converters, adapters, dongles, etc. will prevent the NUC multi monitor feature from working correctly. From our side, the integrated graphics controller and the drivers are working correctly when using straight cables.