NAND veryfication failed for 1 blocks

Hi to everyone,
I'm new to this forum, searched for answers about this kind of problem but I didn't find anything useful.
I'm helping a friend to install HBC into his black Wii (LEH5012xxxxx), but I'm stuck at the backup step done through BootMii, you can see the following logs for both the 0.7 and 0.8 versions of HackMii .

BootMii v1.2.30-g9eea
Stub v
Mini v0.3

Console ID : xxxxxxxx
SysMenu :4.1E boot1v? boot2v4
NAND FS usage : 74.5%

-----------------------------------

Report


BackupMii , NAND ID xxxxxxxx
Free space 1666MB
saved keys for console xxxxxxxx
Uncorrectable page 106548
Uncorrectable page 106549
Uncorrectable page 106550
Uncorrectable page 106551
Factory bad block 1664
Factory bad block 1665
Factory bad block 2642
Factory bad block 2644
Factory bad block 2646
Factory bad block 2648
Backup complete.


Verifying backup...
Press START (Eject) to skip
Verify failed for block 1664
Verify failure for block 1664
Verify failed for 1 blocks
Hit any button to exit.

-----------------------------------------------------------------------

BootMii v1.3
Stub v
Mini v0.4

Console ID : xxxxxxxx
SysMenu :4.1E boot1v? boot2v4
NAND FS usage : 74.5%

-----------------------------------

Report


BackupMii , NAND ID xxxxxxxx
Free space 1666MB
saved keys for console xxxxxxxx
Uncorrectable page 106548
Uncorrectable page 106549
Uncorrectable page 106550
Uncorrectable page 106551
Factory bad block 1664
Factory bad block 1665
Factory bad block 2642
Factory bad block 2644
Factory bad block 2646
Factory bad block 2648
Backup complete.


Verifying backup...
Press START (Eject) to skip
Verify failed for block 1664
Verify failure for block 1664
Verify failed for 1 blocks
Hit any button to exit.


I don't know if my problem can be added in the bugtracker, 'cause in the end the Backupmii find its way to complete, even though it can't verify the saved bin.
Otherwise just tell me and I'll stick this on the proper bug-page.
I have taken 7 backups of the same NAND, one of them freezed on ECC failure when reading the same first bad block, but I was using the original ppcboot.elf from the 0.7 HackMii installer.
After, I used 1 time 0.7 HackMii with the corrected ppcboot.elf and 5 times the 0.8 HackMii, gaining the same 2 type of logs for each BootMii version .
I used two different branded 2GB SD cards, Verbatim and Transced, tried formatting in both FAT and FAT32,with and without other data on them, in this pattern:

1st Verbatim one,FAT,with other data, HM0.8
2nd Verbatim one,backedup data -> FAT format -> resored data, HM0.8
3rd Verbatim one,backedup data -> FAT32 format -> resored data, HM0.8
4th Transcend one just bought,FAT preformatted,re-run HackMii08 and re-prepared SD card,HM0.8
5th Transcend one,backedup data -> FAT32 format -> resored data, HM0.8
6th Transcend one,uninstalled HBC 1.0.8 and BootMii,run HackMii0.7 and installed BootMii/original ppcboot.elf,FAT format SD,freeze,HM0.7
7th Transcend one,swap corrected ppcboot.elf, HM0.7

Side note: fat32 formatted card showed slower NAND reading time on the screen, or may I say slower writing times on the SD?

I have to say that this is not the first time I used HackMii, but it's the first time I run into this.
I searched for some days on the net and I found a few other with the same problem with no real answers, and I'd like to know if this could be a problem restoring that backup in the case of need.
Does "Uncorrectable pages" found in one block of NAND mean that that block isn't completely bad?
I.e. mean that it has only some bad pages instead of being an entire bad block?
If this theory is right, my fear is that maybe sometimes some data could be written in that semi-badblock and cause problems accessing them...what if some bytes of sysmenu or the ios associated with it fall in that pages?
I've not tried to restore a backup made on this console until now, do somebody know how would be treated the backup relating to that block?
Will BootMii write the same uncorrectable pages in the same bad block or completely ignore the uncorrectable pages as marked from a bad block?

Thanks , any suggestion will be appreciated!