Keyframing rubberband bounce

So I've been working on a split screen piece where I have either the whole screen, or just a split screen slide in and out, but when I try to set a slide in and then a slide out, the middle portion of the clip does the Apple bounce like when you scroll to the bottom of the page. What am I doing to cause this?

For example, with the slide in from left to right I'll select the clip, set the starting point at -1920, then in the middle of the clip I'll set another keyframe to 0, everything is fine at this point and the clip stays right in the middle. Then when I go to add the out slide I'll add another key frame about a second after the original 0 keyframe and also set this one to zero, then I set the end of the clip to +1920. Everything works fine in terms of in and out, but the whole section that's supposed to be zero bounces back and forth like a rubberband.

Has anyone else experienced anything like this? I'm using the Tokyo Split Animator, but I have the animations turned off and am only using the plugin for the split screen.

Here's a video of what's happening. Uhh, for some reason YouTube put image stabilization on this video and I can't turn it off, but the bounce happens when the screen goes past the bottom of the frame when it should stop.