Yesterday, I upgraded my desktop to the latest Windows Insider build, 14251. I’ve successfully installed and worked on the previous Fast Ring insider builds over the past few months and I haven’t had any issues.
Unfortunately, this build was the exception. My first clue was Github for Windows telling me there was something wrong with my repository. It was unable to sync. I removed and cloned the repository again, but the error persisted. Running ‘git pull’ and ‘git push’ from the Powershell didn’t seem to do anything, which was odd. So I installed git.exe directly and the installer reported an error. Running git.exe just resulted in a “git has stopped working” message.
I decided not to waste any time on debugging this and I rolled back to the previous build, without issue. Thankfully I was back up and working within an hour.
This experience will temper me in the future and I might just drop back to the Slow Ring 
Tomas McGuinness 