Welcome! Please see the About page for a little more info on how this works.
I can't identify the exact circumstances, but I have seen events where a source code file has been deleted but clojure.tools.namespace.repl/refresh still tries to reload it. Because the file doesn't exist, there's an exception when you try to load it, so you're stuck.
Comment made by: gfredericks
This happens to me pretty frequently, especially when switching branches (which is ironically the best use case for calling {{refresh}}).
Comment made by: stuart.sierra
I still don't know exactly how this occurs.
The workaround for now is to call {{c.t.n.repl/clear}}, added in 0.2.5
yep, noticed that independently and just confirmed that it works.