1000+ "Bad EC magic in block" notifications on NAND boot

Hi, After flashing the NAND drive with a native OpenWRT image, I get a long list of complaints about Bad EC magic blocks. Just over a thousand blocks appear to be bad.

NOTICE:  SPI_NAND Detected ID 0xef
NOTICE:  Page size 2048, Block size 131072, size 268435456
NOTICE:  UBI: scanning [0x200000 - 0x10000000] ...
NOTICE:  UBI: Bad EC magic in block 1008 ffffffff
      .
      .
      .
NOTICE:  UBI: Bad EC magic in block 2010 ffffffff
No size specified -> Using max size (22474752)

I find this disturbing to be sure. But truthfully I’m not sure what it means:

  • Is the NAND damaged?
  • Was there a problem with the flashing process?
  • Is 1000 bad blocks a drop in the bucket, and so nothing to worry about?

Of note, dmesg seems to report PEBs are all good.

root@OpenWrt:~# dmesg | grep bad
[    1.677758] ubi0: good PEBs: 1008, bad PEBs: 0, corrupted PEBs: 0
[    1.699391] ubi0: available PEBs: 0, total reserved PEBs: 1008, PEBs reserved for bad PEB handling: 

Can anyone shed some light on these messages?

Many thanks,