G920P Rebooting after a minute constantly

Ok so after the new Domestic Unlock update was released, I upgraded to Marshmallow, CF-Auto-Root worked fine on the device. The Domestic Unlock was still saying Invalid Sim, so then I downgraded, without doing the full unroot.:mad:

So once I was back on 5.1.1, SuperSU was saying that it was missing the binary, so I did CF-Auto-Root again, but the phone would reboot whenever adb shell tried gaining SU permission. So I tried full unroot, and it said uninstallation failed. So i tried upgrading to Marshmallow again, and then that’s when the device started to reboot every minute.

I tried repartitioning and nand erase all through Odin, without any success. My goal is to be on stock 5.1.1, can somebody PLEASE help me figure this out?? Thanks in advance.