Warning on ubiformat while installing NAND rescue system

[psychokiller]

Hi, while trying to install rescue like described here https://archlinuxarm.org/forum/viewtopic.php?f=30&t=8383&hilit=armv5+rescue#p44875 I get this warning message from ubiformat:
$this->bbcode_second_pass_code('', '
ubiformat: mtd1 (nand), size 133169152 bytes (127.0 MiB), 1016 eraseblocks of 131072 bytes (128.0 KiB), min. I/O size 2048 bytes
libscan: scanning eraseblock 1015 -- 100 % complete
ubiformat: 238 eraseblocks are supposedly empty
ubiformat: warning!: 778 of 1016 eraseblocks contain non-UBI data
ubiformat: continue? (y/N)
')
I actually have UBoot 2016.09-1 installed with a clean environment with two mtd partitions, like reported during boot (dmesg output follows):
$this->bbcode_second_pass_code('', '
[ 12.732269] nand: device found, Manufacturer ID: 0xec, Chip ID: 0xf1
[ 12.738837] nand: Samsung NAND 128MiB 3,3V 8-bit
[ 12.743478] nand: 128 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
[ 12.751096] Scanning device for bad blocks
[ 12.862695] 2 cmdlinepart partitions found on MTD device orion_nand
[ 12.868993] Creating 2 MTD partitions on "orion_nand":
[ 12.874160] 0x000000000000-0x000000100000 : "u-boot"
[ 12.879533] 0x000000100000-0x000008000000 : "rootfs"
')

Before breaking anything, would be safe to answer "Y" to ubiformat and go ahead to format /dev/mtd1 or there is something else I better check before proceeding?

Thanx, Paolo.

[summers]

Well as I haven't installed the rescue system, I'm probably not the person to answer. See what moonman says. But some idle thoughts anyway.

Did you $this->bbcode_second_pass_code('', 'flash_erase') first?

What does $this->bbcode_second_pass_code('', 'dmesg | grep Bad') show? Are the bad blocks where the nand isn't empty? I thought ubi could cope with bad blocks, but I'm not expert ...