If you have your menu/inventory open while you get an item (ie via the NPC hunter fights), the item menu window remains on your screen and your lock-on/camera reset button no longer works while that window is on your screen.
If this happens to you, hitting a load screen fixes it, but note you can't pull switches/climb ladders/open doors, so it may be best to just use a Hunter's Mark to respawn yourself to fix it.