Originally Posted by
astral276
I wasn't suggesting you try to find the one bad item in 4000 as such. More, for example, you export as two lots of 2000 and import each of those. If one goes through and the other fails then the rogue listing is within the group that failed. Split that group again and repeat, eventually (if it is just the one listing) you will end up with a very small group of listings that contains the rogue one.
Of course, it is virtually guaranteed that 5 minutes after completing the exercise the update to NL will appear (if your luck is anything like mine).