Final Cut Pro X: Stabilization may cause flipped video or black bars along the edges
When a clip has extremely shaky camera motion, stabilizing the clip may result in an upside down video image or black bars along the edges of the video.
Follow these stabilization best practices to avoid upside down video or video with black bars along the edges.
In the Video inspector, reduce the value in the appropriate smoothing parameter (Transition, Rotation or Scale) for the stabilization feature.
Cut the clip with the blade tool in the timeline to remove sections with excessive shake or extreme camera moves.
Use the scale transform control in the Video inspector to crop out the black bars of your stabilized video.