The reason sounds dodgy, like a cover up for the real reason.

lumia sales have been not so great, wouldn't suspect nokia it gotta say they break and replace with lumia to clear warehouse

I sense a Gorilla glass stress test coming................

I've not heard of any mass issues with the N9 apart from a batch from Handtec.co.uk (there's a thread on TMO about this). That said, I go my N9 from the same source and have had no problems during my first month.

I digress, the point I'm making is that there have been many issues raised with Nokia support over the Lumia800. I wonder if the OP's issues are related to cross-over hardware between the two devices?

To be fair to Handtec this was not their fault. There are reports of units purchased from other suppliers which also rebooted/crashed heavily. Common factors appear to be 64GB, Austrian product codes, built in Finland.

I had pre-ordered and my first device had major issues. Most attempts to flash failed part way, and when I did manage to perform a flash it made no difference. And when I managed to perform a secure format & flash I found the resulting total capacity to be under 10GB (was originally 64GB!). As if it marked most sectors as bad or something.

I was pleasantly surprised to find Handtec to be very professional in arranging my replacement, which is a Polish variant and works fine, although the lower part of the case does make an unsettling creaking sound when held firmly. Plus display has on occasion displayed odd colours momentarily. The only crash I've experienced was with one of the two Spotify apps, twice. But thankfully no system wide crashes or reboots.

Just received the new device today.everything was legit. Seal was not broken or anything. Going to test this phone for couple days before sending old one back. Our should I just say that I lost it ;P

You could also start some stress tests

Actually I already managed to scratch the screen. I Did not even try to do it.seems to be ready easy to scratch. maybe a waterresistancy next

Funny thing...when I posted link to this thread on Nokia forum, it was immediately removed by moderator.
Nokia is really trying to hide their manufacturing problems (affecting many 64gb black models)
I don't care about official statement because this kind of problem isn't something that manufacturer should talk about too much but lack of internal info is really worrying.
Nokia Poland simply refused to replace my broken n9 argumenting that since Nokia Care said my n9 is fine (they actually broke my n9 even more...) it must be the 'ultimate truth'.
On the other hand Nokia Care admitted, they don't know how to fix n9 - all they know is how to flash it.
Nokia is going down these days...