Going off your video indicates that you're looking in the wrong area in the Spine.
For this week (Strongest Curse | War Chests triumph), the chest is found near the central Tower in the Spine.
[url]https://youtu.be/iHovCq_kVfA?feature=shared[/url]
Time stamp starting at 2:55 will show you the route that you need to follow to find that chest.