I've just replaced my rear seal and its leaking again after only a few days. Its doing my head in too!
The flange seems good, no signs of play, I did a thorough job of fitting the new seal, new felt washer and nut ....
The first seal eventually failed so I replaced it and that one didn't last too long - the seal actually still looked ok, but the felt washer looked like it hadn't seated properly. So I expected that was the reason. Now this one has lasted about 5 days before I've noticed it leaking again