These come from yaffs_ScanBackwards where chunk is calculated as

  chunk = blk * dev->nChunksPerBlock + c

but blk is [1..n] not zero based, so shouldn't it be

  chunk = (blk-1) * ...

(IMHO, egad, you've got some 0 based indexes and some 1 based indexes. 
It's a sure fire way to introduce bugs. For cleanup, you SHOULD move 
everything to 0 based indexes.)

Cal Page