The latest Windows update (last week) broke the ssh-agent in WSL. The ssh client will bluescreen your PC if you make a connection with a key loaded into the agent.
Is it broken in the latest stable release (1809) or preview release (1903)? Anecdotally, I'm running the latest preview release and ssh within WSL is functioning. My ssh-agent does load a key when starting WSL and asks for a password for the key.