WRT3200ACM: ubi2 error

hello community,

one of my WRT3200ACM I have been seeing this error in the syslog (and in dmesg, right after booting):

[   26.555680] ubi2 error: 0xc044fc50: the layout volume was not found
[   26.562057] ubi2 error: 0xc0453584: failed to attach mtd6, error -22

I have no idea what to do with it. Block info shows me:

root@OpenWrt.home:~$ block info
/dev/mtdblock6: TYPE="jffs2"
/dev/mtdblock8: UUID="263926165" VERSION="1" TYPE="ubi"
/dev/mtdblock9: UUID="1122774947" VERSION="1" TYPE="ubi"
/dev/ubiblock0_0: UUID="f63bfda8-24a5f795-1181c070-5fc5daba" VERSION="4.0" MOUNT="/rom" TYPE="squashfs"
/dev/ubi0_1: UUID="e8eb74d5-8d5c-45d9-81e0-95a368c3bc41" VERSION="w4r0" TYPE="ubifs"
/dev/ubi1_0: UUID="7c5bf261-663d-4c59-9a96-9aa2937c517d" VERSION="w4r0" TYPE="ubifs"
/dev/sda1: UUID="fb45d631-bdfe-43d8-b39f-dbe0b25088a7" VERSION="1.0" MOUNT="/overlay" TYPE="ext4"
/dev/sda2: UUID="4d296287-b97a-4368-b05e-efda7524e353" VERSION="1.0" MOUNT="/tmp/log" TYPE="ext4"
/dev/sda3: UUID="e5f99965-7964-40ff-9fdf-aca819e6f36c" VERSION="1.0" MOUNT="/data" TYPE="ext4"
root@OpenWrt.home:~$ block -h

So mtdblock6 is jffs2 - does that mean, that the flash is corrupted? Or is it due to extroot beeing used?Thanks!