Glad you have the file backed up.
You are welcome.
The bootsec.exe /nt60 for a mbr drive is bootsec.exe /nt60 /mbr.
It is a command that I have rarely used.
The bootsec.exe /nt60 may be used for GPT.
Whether that was a source of the problem I would have to look up.
Again I'm glad you got the files backed up as you can now clean install.
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There is a planned release of Windows 10 version 1803 sometime on or after April 10, 2018.