if you want i working solution: return the NUC to the dealer! Intel NUCs have hardware tolerances which are very hard to solve by the BIOS. I am not an engineer, but i have over 20 years of PC experience and a sharpened eye for the reality! And Intel owns just way too much money, then taking their costumers serious. Of course, Intel knows how to produce great CPU and Chipsets. But obviously they do not know how to build a computer and a BIOS. I own a Shuttle DS437 too, and EVERYTHING is woking great out of the box with various OS. Surprise, surprise...
You may have a look for the upcoming Zotac nano C-Series.They pretend to be great...