Serial No. went missing on my MacBook Pro

Hey guys!

Have you ever met this?

I have been recently suffering from nVidia issues on my mid2012 i7 15" MBP. It freezes all the time, have little squares, and lines on screen, when frozen. It wouldn't be a problem, because I have Apple Care, BUT!

As far as I am experiencing these issues, my motherboard forgot it's serial no. It's like if I had already changed my logic board, it says "System Serial#".

I am working with Macs, I am repairing them since 2010, but I've never seen anything like this, and this machine's logic board hasn't been changed, that's for sure, bcz it's my own.

I attach some pictures, where you can see, that hardware monitor app recognizes that I have "switched" computer, but remembers an older machine (with my serial no.), which is quite similar.....

https://www.dropbox.com/sh/0xrdv6o3f700q...