Why my note 5 screen always get stuck after upgrade to Nougat?

[AC Question]

After upgrading to Nougat, my phone always stuck especially when I watched video and when I try to unlock my screen.. it's really annoyed me.. it's still happen even right after I factory reset it and I don't know how to downgrade back to Marshmallow. Please share solution if you have one.

 

[B. Diddy]

Welcome to Android Central! Which app are you using to watch videos? Are these locally saved video files or streaming videos on the web?