While recording rotation for animation, the origin of a piece of an FBX seems to change based on speed of mouse (video)

I feel like I'm losing my mind.

I made a crappy little egg shaped object in blender and it's in two pieces. I drop it in to a scene and plan on animating the thing opening with just a simple position and rotation change for the top and bottom pieces.

While I'm recording keyframes for these things, I get some weirdness in trying to rotate either piece. It seems that based on how fast I move my mouse, the type of rotation I get is different. A quick flick of the mouse will rotate the piece about what I feel is it's origin, but if I'm slowly moving the mouse, the piece begins to do this weird rotation like it's on an invisible ferris wheel. I'm hoping this is simple and maybe it's just me misunderstanding of how rotations work in this regard, but the fact that it only acts funny during the keyframe recording, and it's seemingly dependant on how fast I move my mouse.

If this was an origin problem from blender, I'd imagine that the speed of the mouse would have nothing to do with it, and I'd also expect that it would be messed up when not recording the animation, but that doesn't appear to be the case.

Please have a look at this quick video I took which shows the problem in action: https://www.youtube.com/watch?v=WCmxEj4V-Og

Any help is greatly appreciated.