unreachable corpse in Lost Souls mission in The Fallow Mire

I can't loot the corpse to compete the lost souls (soldiers) quest in the fallow mire. I killed the hand in tactical combat and after the battle I fell from the rafters. I didn't realize I lost something important at first and last my save. Now the corpse and the rusted key I need to progress are stuck in the rafters.

If only I could clip up onto the roof ☹️
Halp

(Xbox One)

Video of the issue
http://youtu.be/pTEcmwWzYcM