I have nxt hd box. It happened a few times with me too after latest update.. I tried a few things. It worked but i dont know exactly which one. U try all.My Screen resolution changing to 720p after every re-start...i have to change it to 1080p after every boot...any solution to keep it as 1080p always?using HDMI only.
1. Factory reset stb from stb settings
2. Force download software update. Try from setting. If it donot work then power off stb from switch board. Now press stb power button and keep it pressed then turn on stb power from switch board. Force software update will start. U can release stb power button once software upgrade starts.