It has something to do with a LTE bug, many people have had it. I actually have it currently on my S3 with Quantum ROM.
From what I have found and read is that we have to go back to stock ROM, though it is "complicated" that it might brick our phones with an increased percentage... I am looking for guides on helping me go back to stock, but everything is so unorganized on here and many more experienced users don't like to help others who have problems. They just tell us what is needed without the aide that might help prevent a brick..
What I do know is that you need to go back to an old bootloader but you can't go back to an old bootloader..
I will be following this thread for some help, mine didn't get any help.