[Yaffs] Concerned about partially written block detected

On an ARM board, running yaffs2 from NAND, it boots up OK, but every
time, I keep seeing more and more of these messages in the kernel
dmesg output:

Partially written block NNN detected

NNN is the same number, for about 10 lines in a row.

Then, it becomes another number, and prints another 10-or-so lines in a row.

I'm concerned about this, because as I keep rebooting the system, more
and more lines like this appear. I check "dmesg" after each boot.
Since this is an embedded system, it can never be cleanly shut down.
I hope that yaffs2 doesn't have a problem dealing with dirty
shutdowns.

Is this normal? I thought that yaffs2 was supposed to recover from
partially written blocks, and reuse those blocks eventually once
garbage collection takes place. I'm concerned about losing NAND
capacity over time, as eventually, every block will be partially
written, as this ARM board will always be rudely powered off (never
cleanly shut down).

Is there anything that I should do, to solve the problem of more and
more of these lines appearing in dmesg over time? Is there some kind
of "yaffs2 fsck" program that needs to be ran periodically, to clean
up the filesystem, and reclaim these partially written blocks?

Thanks!

Josh