Ok I checked.
This is not an issue since it is working as intended.
The reason for the fixed positioning is to have the batch-items be fixed to the very bottom of the browser viewport when there is a lot of empty vertical whitespace.
If you resize vertically you’ll notice the fixed class gets attached when there is a significant amount of vertical white space. This ensure the batch-items is always positioned in the same spot for easy access.
The fixed class gets detached when the rendered content view exceeds the viewport.
Video to illustrate the attach/detach of batch-items: http://recordit.co/lQPF8UKeqF
Looks like the reorder embed needs a bottom margin to clear the fixed batch-items. That is your solution.