Dang.
Suddenly, the UD7 will not boot off of the ESP partition. It worked a few weeks ago, when the drive was on a differnt port. I hope I dont have to open the case and switch SATA ports or something. I'll look again in the mobo GUI for relevent settings.
That did not work.
 I'll reinstall Clover 1913, and if no luck, I'll open the case.
Opening the case is a big deal on this machine. The mass is at least 34 kilos (75 lbs)  and must be deinstalled from a custom self, and hoisted onto a workbench. The drive "works" fine, so it is an unpleasant surprise to find it will  not boot in the current config.