There seems to be a bug in Sea of Clouds (not sure if it happens anywhere else) that when you pull a mob that is not chained to anything it will chain link itself to a mob WAY above it causing it to walk off the edge and float it's way down.
Not sure how else to describe this so I made 2 videos to show you:
(The titles of the videos are the coords that it took place.)
https://www.youtube.com/watch?v=XtjlpMCwy2c
https://www.youtube.com/watch?v=G5ugS3k3N1Y