Windows 10 can stop working and it is usually through apps and software that I encourage people NOT to use.
If windows 10 fails to boot as a recent clients did you will have to boot Windows into recovery mode , reset Windows 10 then load a new copy of Windows 10 but leave your documents on Windows 10.
You will then have to reinstall your programs ( yes i know its a nuisance but you did the wrong thing initially)
So what programs did this client install on their computer , ones that they did not need and ones that obviously have an issue. I have highlighted them in red.
Stop installing programs that you do not need , let Microsoft handle Microsoft issues and do not look for the mystery fix as most of the above programs are.