Slow Motion Footage - Poor Quality Export

Greetings,

I know its no where near a professional camera, but I've been importing some slow motion footage taken with my Canon S100. The original file out of the camera is MPEG-4 AVC - 640x480 @ 29.97 fps, 10.2 Mbps. It's actually capturing at 120fps.

When I use any of these clips in a Final Cut Pro X project, when I export the project, the slow motion clip always looks horrible. The rest of the regular 1080 footage from this pocket camera looks fine, its just the slow motion segments that are horribly compressed. I've tried export to "Apple Devices", exporting media to H264, just about everything - similar poor results.

When I transcode the original into "Optimized" media, I opened the Optimized file in Finder and it looked fine. When I created a Proxy version, it looked terrible.

Just to test, I ran the original media through Handbrake to a .mp4 H264 and the transcoded video looked fine. So its only after it passes through Final Cut that it looks bad.

Below are some screenshots of an original clip followed by an FCPX exported version.

Screenshot of original media

Screenshot of project output (in this case, .H264)

Any thoughts?