If you look in yaffs_WriteDataToFile where

nBytesRead = in->variant.fileVariant.fileSize - 
(chunk-1)*dev->nDataBytesPerChunk

shouldn't chunk be -2 instead?

If I do that, the lengths get calculated properly, and the data is 
written properly to the disk.

Leaving it at -1 means that the +verify-all check fails on the first 
file write to the nand.

Cal Page