Unable to update unrooted phone to latest version

I have never rooted or flashed a ROM on to this phone. When I try to update (OTA) from G900AUCU4BOF2 to G900AUCU4BOF3 (fixing stagefright), it does not update. I can download the update fully and my phone restarts but when it is installing the update fails at 28%. I have wiped my cache and booted into safe mode but it still fails.