In the video frame above select the Positive vs Negative trial and measure the force as a function of distance.

Fit a line to ONLY the data points where the force is less than $0\mathrm{.}002N.($you can easily remove a point from the linear fit by clicking on the point on the graph itself$).$

What is the relationship between the distance between the spheres and the force on the spheres? What is your evidence?

Do the data points from the end of the video $($when Force $>0\mathrm{.}002N)$ lie above the trend line or below the trend line established by the data points from the first part fo the video?

Does this new result allow you to rule out any of your tentative explanations?

If you can rule out all of your provisional explanations except for one, then that one might be a great candidate for being the correct answer.