A number of other users have had these issues and others that I have helped either privately or on a forum and this method also worked out for them too so I thought id share it here for anybody else to try.
Basically my line of thought is that the last 412 update also included core system updates that prepares the handset for 4.3 but at the end of the day i dont know why the success but it has helped
Bear in mind that this will only work if you have MJ9 installed or older, newer bootloaders wont allow downgrading.
First download all the files below on your pc and make sure the samsung usb drivers are installed. Also download the rom you wish to flash.
1) put phone in download mode (vol down + home + power) and use odin pda tab to flash the blpatch
2) use pda tab in odin to flash dmg1
3) boot phone to setup screen
4) put back in download mode and flash the MJ5 BL with the pda tab
5) flash TWRP with pda tab
6) boot to TWRP (vol up + home + power) to flash rom.
7) hit thanks or buy me a beer
Twrp Odin Http://goo.gl/SSyv53
MJ5 BL Http://goo.gl/95w2ev
Thanks goes to @T.G.A @morr_1228 @ecsjjgg and a few others I cant find right now for running the process and basically confirming it worked for them too