I337UCUEMK2 (Android 4.3) - Official Samsung Version
I wanted to do a factory reset/cache clear on my phone in an attempt to fix lag experienced when using my phone which got really bad this morning, so I tried to boot into Recovery Mode (Volume Up + Home + Power). It acts like it's going to but then just goes strait into download mode and says "Downloading... Do not turn off target!!", not the normal warning about loading a custom OS and volume up to continue/down to cancel.
I've tried to flash the original ROM and even some custom ROMs using ODIN which keeps failing at the NAND write stage giving the FAIL (auth) error.
Now when booting my phone shows Samsung Custom with an open padlock but otherwise works fine.
At the top of the screen in download mode it says:
Could not do normal boot.
PRODUCT NAME: SGH-I337
CURRENT BINARY: Samsung Official
SYSTEM STATUS: Custom
KNOX KERNEL LOCK: 0x0
KNOCK WARRANTY VOID: 0x0
WRITE PROTECTION: Enable
eMMC BURST MODE enabled
I couldn't find anything during some searches both on Google and here. What should I do?