Thank you Paula!
No, that seems to be resolved. I used it in aperture priority mode during this trip but have used it quite a bit on land in manual mode and had no problem with the screen blacking out.
Focus, incidentally, worked without focus light, even inside wrecks and caves in complete darkness.
The question about the screen going dark applies only when you are setting the manual mode for a dark background while you are using the strobe for the light source. If you set your camera to be several stops underexposed, does the screen also turn dark?