I have read on the internet that the start menu problem happens to user accounts that where previously on Windows 7 and then used the free upgrade to windows 10 but kept the same user account.
I have this problem. For me the Start menu and Cortana stop working and all sound output from my PC stops. For some reason this happens to me with random games after a few minutes of playing. It has happened with Fallout 4 most frequently for me but has also happened with other games although never with KSP. Restarting my PC (full turn off by holding power button) seems to fix it and the game works normally then.
An apparent fix is creating a new user account in Windows 10. I haven't tried it so I can't confirm if it works or not.
Good luck with your upgrade and hope you don't counter any problems.
As your avatar man once said, ''There are two kind of people; Those with problems, and those without.''