It works for me. Can you provide more detailed steps about exactly what you are doing?
Please also remember to include the exact text of any error messages that appear. In this case you refer to "crashes", which should include some information about the problem in error messages, but since I can't reproduce the problem I don't know what that information is.
Note you use save and load inefficiently. 'A is down' is true every tick, so you're saving 60 times a second while the A key is down, and similarly loading 60 times a second while the D key is down. You should replace them with 'On key pressed' triggers.