Hi Patrick, sorry for begin a slow responder.
Please upgrade to latest just to make sure you are not hit by any trouble in an earlier version. There have been some trouble with late coming routes — actually some cases is first handled properly in 15.4
I had skim of your code, couldn't actually discover the problem immediately, I recommend debugging seeing how far things gets.
Maybe it helps to inform that the 'not found' route's path is set to ´**´, so it might hint that the routes you defined did not give a match with your URL?
— I do not think that the 'late coming routes' is a problem in regards to your Workspace Routes(routes.setRoutes), as the Not Found route are first added as part of your call to 'setRoutes'.
But its worth noticing that there is two levels of Routers in play here. One for the Workspace and then one for the Workspace Editor(Handling the Workspace Views). So please investigate which of them if falling back to Not Found.