Yea, that's an old radio from like almost 2 years ago. They were not known as being the most reliable for LTE stuff. If you aren't S-off then my suggestion is to relock the bootloader then RUU to the newest 4.3 (backup your storage to the PC first because I think it wipes it due to needing to repartition for the 4.3 update since the system is bigger). This has the newest radio and touchscreen firmware as well as allowing you to run newer versions of the roms you like. You'll have to redo the bootloader unlock and recovery, but it's the same process as before. If you are S-Off then you might be able to just skip the RUU and flash the firmware package only.
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