I have had the same problem and had 2 new sets of hinges replaced by NEFF.
The problem reoccured so I took the door apart, re seated the hinges and replaced and have not had a problem since.
It would appear that this is a poor design issue, which you would expect NEFF to resolve FOC and permanently rather than constantly sending out hinges.
I have checked the 2 pairs that were replaced and there is minimal wear on them so I do not think a new hinge is necessarily the answer.
Only took 30 mins or so to replace the hinges, once you figure out how simple it is to lift off the door, which is only held in by weight and a bit of friction and spring tension. Altogther a bit fiddly.
If you have not sorted this yet, reply back and I'll try to guide you on best way to approach the work if you do want to replace them
Alan Pougher
November 2009