I recently upgraded to Firmware 5S0J from 5S0D and noticed that the error correction has very poor performance compared to 5S0D. I tried to downgrade but this f**ing windows flasher complained(I think you all know what about.). Anyway, I tried to patch the exe-file so it doesn't complain anymore, and it worked! I found out that you got to change the following offsets via a hex editor(use HexWorkshop or similar):
4F6F: 85 --> 84
4F7C: 85 --> 84
As for now, all the windows firmware updates have the same size, so the offsets to be changed are always the same!
If done, you can flash as usual.