Repair Windows 10, MacOS High Sierra?

MBP late 2013, macOS Sierra, with Bootcamp Win10, and updated at one of the last High Sierra Public Betas.

And now my Windows 10 does not boot anymore. It does not even get as far as display any windows 10 boot screen. It locks show an underscore in the upper left corner of the screen.

Not sure whether it is possible to repair a bootcamp windows 10 without damaging the macOS boot?