If you see 0xFF repeated for an entire 64KB block, that sector was marked as "dirty" in the 6531e's FTL. The file is still valid, but that section contains no data.
any existing data, as flashing will wipe the device completely. 6531e w25q32bv flash file
If the IMEI is invalid, a flashing tool with IMEI repair functionality is required after flashing. If you see 0xFF repeated for an entire