There are too many of these small bodies out there all exhibiting the same or nearly same weird behavior. With the new WFIRST and other infrared survey telescopes looking for asteroids, if there is something large out there that is causing the orbital scattering they will find it or have to go back to the math calculations.
THIS is the thing I keep pinned to the back of my brain: There are a number of objects out there that should have done one thing, and haven't, and show oddly similar patterns of behavior, and shouldn't. So the current 'best idea' is that there is a bigger something out there, that is dark and hard to see, and is causing these other - necessarily smaller - things to act in a similar manner. Due to my lack of expertise in astrophysics, until the behavior of these bodies can be explained by an alternate hypothesis (which this one doesn't seem to address), I think I'm going to stick with Planet X.