I don't think Windows Repair should be run on an Insider Preview because of its Beta qualities.
Shane has already disabled certain repairs in the program because of changes made to the registry following the Fall Creators Update in the released version.
You may be able to use your restore points if System protection is turned on.
To get to those, from the cmd prompt enter rstrui.exe and then you can see if there are any restore points.
From the cmd prompt you could also try a chkdsk /f, an offboot sfc /scannow as well as the bootrec cmds.
Enter bcdedit |find "osdevice" and using the partition letter instead of the X I've used, enter the following cmd -
chkdsk x: /f
Follow that with this cmd, again using your partition letter instead of X
sfc /scannow /offbootdir=X:\ /offwindir=X:\Windows
For clarity, that is a Pipe symbol before find and is the uppercase of \ and note there is a space before each /
There are three bootrec cmds you can run and they are -
bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd
You may get an error message with the /fixboot one - I do and the /rebuildbcd will look for volumes on your machine.
If you have a Windows.old on there then it will return 1 and do you want to include that - enter n
If it returns as 0 then enter y
If your machine dual boots with any other OS then don't run the /rebuildbcd.
