It is important to note that the dev 39 chip does not solve all the sha errors. SHA errors mean that the contents of the flash memory do not agree with the original program's content. This usually means areas of the nand are corrupt or bad. The dev 39 chip bypasses this test, and if you had a working board before, it is likely that just a few bits are off and you won't have noticeable issues. But if you got a board that was SHA from the beginning and you had no clue where it came from, the dev 39 chip does not guarantee that you will have a trouble free experience.