I doubt that a fix to the API will be along anytime soon. What is really needed is a new API which connects to the new data structures and features. Tasks, Calendars, Note Update etc all need new options in the API.
In layman's language the old API requires the Legacy connections and what most applications do is connect as Legacy. However, the real time sync has to lock the Legacy data while RTE/Sync is connected so many external applications are effectively locked out and generate errors.
I don't think that there is a solution for this other than the release of a new API. My backup utility still works because, I think, I shutdown all Evernote access overnight when it happens I have the backup scheduled to run.