Hi Sylvia,
Thank you for getting back to me.
I tested with an old Sony 1024x768 monitor and there were no issues.
However the monitor that shows problems with the motherboard is a Dell 1920x1200, aspect 16:10.
As the Dell didn't have issues with a few different motherboards it looks like DH87RL just cannot handle this resolution/aspect ratio correctly during POST. Maybe a fix in the future BIOS release?
Kind regards,
Alex