We sold 4 NUCs to customes and all have the same issue, when using HDMI to VGA or HDMI to DVI adapter then picture blinks every 2-3 seconds.
When HDMI connected directly - no problems.
We ordered USB-C to DVI adapters as a workaround.
BIOS and HDMI firmware are the latest.
Any solution to this problem?
You mentioned that HDMI output from NUC works as expected. Therefore in my opinion, this problem is not caused by NUC. It looks like the VGA/DVI displays are going out of sync. Did you tried to lower the Display Refresh Rate to 30Hz and/or lower the Display resolution? Please check if the video output signal resolution and refresh rate, corresponds to the monitor default/requirements.