Did the steps 1-3 and also tried DeskScapes with static background as opposed to the video moving type backgrounds.
In all cases, static img or otherwise, when DeskScapes is running the Fences snapshot results in black background image with just the Fences showing in their correct positions.
As soon as DeskScapes is disabled and a Windows background is applied, the snapshot in Fences shows the background and Fences positions correctly.
Just an observation, when disabling DeskScapes (via the settings on lower left and selecting 'Disable DeskScapes') the screens go to solid black, solid colour. If memory serves, a long time back with earlier versions of DeskScapes when turning it off would default back to the Windows Image desktop. Just wondering if this indicates a link to the issue?