I just bought a Nano as well, thinking that I would be safe by now with it having the newer extractor/ejector. However, I am not sure as my serial # is NU003XXX.
The best I could find was ones built in early spring of this year would be fine (around 6000 plus). Yours in the 14-15K range should be GTG.
I shot over a 100 rounds in my mine last week with a total of 4 FTE on Winchester white box 115. None on 124 or 147 self defence rounds (probably 30-40 of those) that I shot at the beginning of the session.
I will keep shooting it to see if the FTE continue with the cheap stuff and then decide if it needs to go back to Beretta or not.
I feel kind of dumb not checking the serial number before buying it to make sure it was a newer one. But there are plenty of guys with very low serial numbers that have had no FTE or issues at all.