Someone posted they had this problem a month or so ago, - even with the correct gas. I had exactly the same problem, - dealer couldnt find any problem, said it must be gas, - it wasnt, - always used at least a 92 octane, usually 94.
Escalated the problem with Nissan, and to make the long story short, the problem has been solved when they replaced ALL 6 Ignition coils!
Dont know why, - but the car doesnt knock anymore.

Bill