It looks like either the Super I/O chip on that board is not actually a Winbond W836xx, the flash chip isn't connected to that super IO, or you have a flash chip that isn't yet supported by flashrom. The reason I say this is because the technical manual says it uses a National Semiconductor PC87427, and that would explain the odd errors from flashrom. Do you have physical access to one of these boards? If so, can you get the part numbers off the Super I/O and BIOS flash chips?
-Corey