before flashing nut's rom, did you flash the first step by flashtool?
are both of you Z or ZL? so far the 307 update is only for Z
some more if you check and check, it won't say that 307 is available. you simply just start updating, and it will say that you are updated to 307.

My preference is XZL as it serves my need as daily driver and as for me it not necessary to have Water/Dust Proof device..

So far XZL are really good design, well build, not that big compare to XZ.
One thing I liked the most is the LED light in XZL, it looks as THE EYE..

After 3 months using XPZ with black dot at lens defect, finally I sent for warranty claim at Sony today. They promises to replace new set for me next week. I'm happy.

That isn't dust. Googling the issue, you'll find more users with the same complaint. A user in forum XDA sent his unit in, and the camera lens / sensor was replaced under warranty. However, because they had to dissamble his phone, it lost it's waterproof capabilities. He submerged his phone in the water , and his phone 'drowned'.

This is a known issue and is affecting many people. It is not a software defect nor is it due to accumulation of dust. Some say that if you turn on the image stabilization future, the black dots would start to move.

Some members claim that instead of their units being repaired, they're getting replacements. Depends on the luck. AP set users, are sadly out of luck. 

Yes, u can go any Sony Service Centre..Bring a long ur warranty and receipt..

Any games to recommend me to play? Got too many memory now.. I just noticed my papago was downloaded to external sdcard but not internal memory.. Then just download zombie frontier 2, ironman, richman, temple run, subway those mini games.. Anyone can recommend some nice and easy play d game? Just sometime I wish to pass my time..for 15 minutes to 30minutee only for most.. Normally I play candy crush only.. Jus feel want to full up the internal memory.. Lol