I'm in exactly the same boat.
I had to provide a NSC form for one of my family members, I assume that this is what is taking so long, but still sitting and waiting.
PR submitted 2 Dec, 2021
Acknowledged 24 Jan 2022
INZ1209 submitted and acknowledged on 25 Jan 2022
and it's in a black hole of nothingness.
I did get a helpful reply 2 months ago from a manager at Palmerston North, basically saying "it's with third party checking, and I can't go into any more detail"...and then no response to my reply.
<sigh>