yaffs_CheckpointFindNextCheckpointBlock :

   dev->readChunkWithTagsFromNAND(dev,realignedChunk,NULL,&tags);
   if(tags.sequenceNumber == YAFFS_SEQUENCE_CHECKPOINT_DATA)
{
  ......
}

If this block is  "bad block", the tags seq  value may equal to
YAFFS_SEQUENCE_CHECKPOINT_DATA , so yaffs stop read checkpoint data
from the real
checkpoint block.
Any tips?