Also, for times it crashes in the middle of the map this is what you could do:
Well, when a server crashes the plugin_end() wouldn't execute right?
So each time plugin_end() executes, you could write something to vault saying that the server successfully shut down the map.
Now if it crashes after a map change, it's usually to a bad WAD file or too many precached textures, in which case (at least on Windows) the server will not automatically restart until someone hits "OK" for the error message, so you could just compare the time it takes for the map to change like PM said.