Summary

From my previous modified track:
https://www.thingiverse.com/thing:3710272
The rubber band fall off quite often when making a quick turn or rotating, so I made this version by using multiple (tiny) rubber bands. Due to the limitted space, I only installed 8 rubber bands for each side. It is easier to install the rubber band from sideway as show in the picture. The rubber bands also add tension to the tracks. This version works much better than the previous one.

https://www.youtube.com/watch?v=TNe0AQeoZTI&feature=youtu.be

https://www.youtube.com/watch?v=XYGToFJ_LnU