It appears there is still no resolution to this? I'm running 10.4.3 Build 2071 and getting the dreaded "Failed to Export Notes" message.
I'd like to try @Matthias Dannenberger's solution but I can't find where to download the "legacy app". If you could provide that information, @Matthias Dannenberger, I'd love to try your fix.
Otherwise, I hope someone at Evernote is reading this and addressing the problem.
This was a really bad way to release such a major change. Ditto, @Matthias Dannenberger, "Shame on you Evernote Team!"