Quite surprised that someone replies to an issue with an "I have no problem so there is no problem". Many of us pay money to evernote to store there all our knowledge and data so if people cannot back it up and has a thread for years that must be something to check, not to ignore or negate.
I have 3k notes and I used to do these backups every few months, now Im facing the same problem. Tried all what you said and the only thing that worked was to split it in 10 exports of about ~300 notes each one.
I would expect Evernote to change this, or to put a web download for everything, but