: If you are modifying the file yourself before writing, importing it into WinOLS with the "calculate compatibility test checksum" option checked can cause errors during the subsequent write attempt.
How to Fix “Checksum Error Writing Buffer” on KESS V2 (Verified Solutions) checksum error writing buffer kess v2 verified
Compare your original "ORI" file and your "MOD" file. They must be the exact same size down to the byte. If your tuner sent a compressed file or a file with a different extension (like .txt instead of .bin), the buffer will reject it. : If you are modifying the file yourself