To jeffreii
I have the same problem but mine is international version, no carrier like AT&T. And yep. You are right. I flash s4 to 4.4.2 and then try to flash back to 4.3. I couldn't so I searched and one forum says install the custom recovery and then factory reset using recovery mode. But after I install, I couldn't boot the phone nor call recovery mode. Then, I go to mobile service and they install 4.2, the original version i.e the same version as when it was bought. Finally, the phone reboot. But, it has network error and can't make any call. Plus, in odin mode, it says custom. knox void 1.
So first I would like to fix that.
Second I would like to flash 4.3 back if possible.
I would very much appreciate your help.